Authors:Shang Sun; Zhenxing Zhou, Chen Zhang, Wenhong Yang, Qinghai Song, Shumin Xiao Abstract: Wide-bandgap material based all-dielectric metasurfaces have been ideal platforms for the realization of arbitrary phase control in visible spectrum. While TiO2 metasurfaces are very promising in broadband and high-efficiency anomalous transmission, meta-hologram, and meta-lenses et al., the current realizations are strongly dependent on the sophisticated fabrication technique to fabricate TiO2 nano-pillars with aspect ratio > 10. Herein we experimentally demonstrate a much simpler approach to realize efficient phase control of visible light. By exploiting TiO2 nano-blocks as meta-atoms on a ground metal plane, we find that TiO2 metasurface with aspect ratio around 1-1.5 is good enough to produce phase changes covering -π to π and high reflection efficiency simultaneously. Based on the phase control of the meta-reflectarray, anomalous reflection with a ratio between anomalous reflection and normal reflection ∼ 74/26 have been experimentally realized using a combination of typical electron-beam lithography, electron-beam evaporation, and a simple lift-off process. Similarly, high performance TiO2 metasurface in form of hologram has also been demonstrated for red (633 nm), green (520 nm), and blue (445 nm) wavelengths. We believe this research shall route a new way to cost-effective all-dielectric metasurfaces and advance their applications in encryption, anti-counterfeiting, and wearable displays.In our study, TiO2 nano-blocks as meta-atoms on a ground metal plane with aspect ratio around 1-1.5 can provide efficient full phase control. Using a combination of typical electron-beam lithography, electron-beam evaporation, and a simple lift-off process, high performance TiO2 metasurface in form of anomalous reflection and hologram has been demonstrated for visible wavelengths. PubDate: 2017-12-07T09:13:06.665714-05: DOI: 10.1002/andp.201700418

Authors:Vidar Gudmundsson; Nzar Rauf Abdulla, Anna Sitek, Hsi-Sheng Goan, Chi-Shung Tang, Andrei Manolescu Abstract: We show that a Rabi-splitting of the states of strongly interacting electrons in parallel quantum dots embedded in a short quantum wire placed in a photon cavity can be produced by either the para- or the dia-magnetic electron-photon interactions when the geometry of the system is properly accounted for and the photon field is tuned close to a resonance with the electron system. We use these two resonances to explore the electroluminescence caused by the transport of electrons through the one- and two-electron ground states of the system and their corresponding conventional and vacuum electroluminescense as the central system is opened up by coupling it to external leads acting as electron reservoirs. Our analysis indicates that high-order electron-photon processes are necessary to adequately construct the cavity-photon dressed electron states needed to describe both types of electroluminescence.The authors study both the conventional and the ground state electroluminescence caused by electron transport through an anisotropic multi level system of two parallel quantum dots in a photon cavity as the electron-photon interaction is enhanced by a Rabi resonance caused either by the usual para- or the less used diamagnetic interaction. The type of the Rabi resonance is chosen by the polarization of the cavity photons. PubDate: 2017-12-07T05:42:30.27688-05:0 DOI: 10.1002/andp.201700334

Abstract: A polarization multiplexed scheme is presented by Xiaohu Zhang, Mingbo Pu, and co-workers in article number andp.201700248R1. The polarization encryption information is encoded in metasurface and decoded by special filter after the sample. The multicolor holographic display is also realized by combining the broadband characteristic with polarization dependence of the anisotropic metasurface. The proposed method is promising for multicolor display, multifunction device and encryption technology etc. PubDate: 2017-12-04T06:26:05.062841-05: DOI: 10.1002/andp.201770104

Abstract: The cover illustrates a novel structured optical field, named as the circular optical vortex array. The top layer shows the three-dimensional intensity distribution of a special example, on which the topological charges (dark points) of the inner and outer circles are +1 and −1, respectively. The bottom layer demonstrates the corresponding phase distribution of the top intensity. These two layers are linked by four lines, in which the red and yellow lines represent the positions of the positive and negative vortices, respectively. PubDate: 2017-12-04T06:26:03.448299-05: DOI: 10.1002/andp.201770100

Authors:Kwang-Hyon Kim Abstract: This work reports giant optical nonlinearity of active gain composites containing metal nanoparticles. In the epsilon-near-zero regime, the effective index of the composite strongly depends on the magnitude of host material's saturable gain and one can obtain unity-order nonlinear optical index change for the pump with gain saturation intensity. For pump intensity of about 100 kW/cm2, the nonlinear refractive index (the refractive index change per unit pump intensity) reaches 10−5 cm2/W, which is 6–8 orders-of-magnitude larger than the records recently obtained in epsilon-near-zero bulk materials. If the gain value of the host medium is slightly larger than a critical value, such large optical nonlinearity can be obtained without loss or even accompanying with amplification. The proposed materials also have the advantage of wide tunability of operating wavelength range from visible to infrared by changing the gain value of the host and the shape parameters and filling factors of metal nanoparticles.In epsilon-near-zero regime, the effective indices of dye-doped dielectric composites containing metal nanoparticles strongly depend on the saturable gain of host material and one can obtain unity-order index change for pump intensity of about 100 kW/cm2. Nonlinear refractive index reaches 10−5 cm2/W, 6–8 orders-of-magnitude larger than the recently reported records. By properly adjusting the gain of the host, such nonlinearity can be obtained without loss or even accompanying with amplification. PubDate: 2017-11-29T07:36:18.484223-05: DOI: 10.1002/andp.201700259

Authors:Zhong-Xiao Wang; Yong-Pan Gao, Tie-Jun Wang, Chuan Wang Abstract: Gaussian steering is used to characterize the intrinsic quantum correlation of Gaussian states under Gaussian measurement. Here we study the generation of one-way Gaussian steering and the conversion of one-way Gaussian steering. It is found that one-way Gaussian steering could be generated by using Gaussian channels, either the Gaussian lossy channel or the Gaussian amplification channel. Exploiting the one-way Gaussian steering in a two-partite quantum system consists of two subsystems marked with A and B, one-way Gaussian steering (steering from A to B) can be converted to the other one-way Gaussian steering (steering from B to A) using linear optics, and vice versa.Here the generation of one-way Gaussian steering and the conversion of one-way Gaussian steering could be realized using linear optics. The one-way Gaussian steering could be generated by using Gaussian channels, either the Gaussian lossy channel or the Gaussian amplification channel. Exploiting the one-way Gaussian steering in a two-partite quantum system consists of two subsystems marked with A and B, one-way Gaussian steering (steering from A to B) can be converted to the other one-way Gaussian steering (steering from B to A) using linear optics, and vice versa. PubDate: 2017-11-28T09:26:12.708266-05: DOI: 10.1002/andp.201700328

Authors:Rafael Augusto Couceiro Correa; Davi Monteiro Dantas, Pedro Henrique Ribeiro da Silva Moraes, Alvaro Souza Dutra, Carlos Alberto Santos Almeida Abstract: This work aims to analyse the so-called configurational entropy in the Weyl pure geometrical thick brane model. The Weyl structure plays a prominent role in the brane thickness of this model. We find a set of parameters associated to the brane width where the configurational entropy exhibits critical points. The information-theoretical measure sets bounds into parameter of Weyl pure geometrical brane model. In addition, we also argue that a similar approach can be useful to analyze the corrections to Newtonian and Coulombian potentials in Weyl scenarios.In this work, we study the configurational entropy (CE) in the Weyl pure geometrical thick brane model. The Weyl structure plays a prominent role in the brane thickness of this model. This graphical abstract denotes the brighter areas where the model parameters denote unstable points (maximum CE), while the darken regions denote stable points (minimum CE). PubDate: 2017-11-28T09:22:03.89461-05:0 DOI: 10.1002/andp.201700188

Authors:Mina Noori; Mohammad Soroosh, Hamed Baghban Abstract: A comprehensive review considering recent advances in self-collimation and its applications in optical integration is covered in the current article. Self-collimation is compared to the conventional technique of photonic bandgap engineering to control the light propagation in photonic crystal-based structures. It is fully discussed how the self-collimation phenomenon can be tailored to be independent of the incident angle and polarization. This adds substantial flexibility to the structure to overcome light coupling challenges and simultaneously aids in the omission of bulk and challenging elements, including polarizers and lenses from optical integrated circuits. Additionally, designed structures have the potential to be rescaled to operate in any desired frequency range thanks to the scalability rule in the field of electromagnetics. Moreover, it is shown that one can boost the coupling efficiency by applying an anti-reflection property to the structure, which provides not only efficient index matching but also the matching between external waves with uniform amplitude and Bloch waves with periodic amplitude.Here, a comprehensive review of recent advances in self-collimation and its importance in optical integration is covered. Self-collimation is compared to photonic band gap engineering in photonic crystal structures. It is also discussed how self-collimation phenomenon can be engineered to be independent of incident angle and polarization. Moreover, it is shown that coupling efficiency can be enhanced by applying anti-reflection to the structure which provides efficient index matching mechanism. PubDate: 2017-11-28T09:21:48.572309-05: DOI: 10.1002/andp.201700049

Authors:Robert J. Nemiroff Abstract: When an object moves faster than emissions it creates, it may appear at two positions simultaneously. The appearance or disappearance of this bifurcation is referred to as a pair event. Inherently convolved with superluminal motion, pair events have no subluminal counterparts. Common examples of superluminal motions that exhibit pair events include Cherenkov radiation, sonic booms, illumination fronts from variable light sources, and rotating beams. The minimally simple case of pair events from a single massive object is explored here: uniform linear motion. A pair event is perceived when the radial component of the object's speed toward the observer drops from superluminal to subluminal. Emission from the pair creation event will reach the observer before emission from either of the two images created. Potentially observable image pair events are described for sonic booms and Cherenkov light. To date, no detection of discrete images following a projectile pair event have ever been reported, and so the pair event nature of sonic booms and Cherenkov radiation, for example, remains unconfirmed. Recent advances in modern technology have made such pair event tracking feasible. If measured, pair events could provide important information about object distance and history.To an observer, a passing object moving faster than emissions it creates is shown to appear at two positions at once. Discussed examples include Cherenkov radiation and supersonic airplanes. PubDate: 2017-11-28T09:20:28.018944-05: DOI: 10.1002/andp.201700333

Authors:Alexander Jarjour; Jon W. Cox, William T. Ruane, Holger Wenckstern, Marius Grundmann, Leonard J. Brillson Abstract: Ohmic and rectifying metal contacts to semiconductor nanowires are integral to electronic device structures and typically require different metals and different process techniques to form. Here we show how a noble metal ion beam of Pt commonly used to pattern conducting contacts in electron microscopes can form both ohmic and Schottky/blocking contacts on ZnO nanowires by controlling native point defects at the intimate metal-semiconductor interface. Spatially-resolved cathodoluminescence spectroscopy on a nanoscale both laterally and in depth gauges the nature, density, and spatial distribution of specific native point defects inside the nanowires and at their metal interfaces. Combinations of electron and ion beam deposition, annealing, and sculpting of the same nanowire provide either low contact resistivity ohmic contacts or a high Schottky/blocking barrier with a single metal source. These results highlight the importance of native point defects distributed inside nanowires and their variation near interfaces with sculpting and annealing.Native point defects inside ZnO nanowires can be used to produce both ohmic and Schottky contact behaviors from a single applied metal on the same nanowire. Besides highlighting the importance of defects and advancing our understanding of metal contacts to nanowires, it demonstrates how scanning electron microscopes equipped with just Pt gas injection can produce both types of contacts without the need to pattern multiple metal deposits or implant dopants. PubDate: 2017-11-28T09:15:51.076152-05: DOI: 10.1002/andp.201700335

Authors:Pedro Schlottmann Abstract: The nesting of the Fermi surfaces of an electron and a hole pocket separated by a vector Q commensurate with the lattice in conjunction with the interaction between the quasiparticles can give rise to a rich phase diagram. Of particular importance is itinerant antiferromagnetic order in the context of pnictides and heavy fermion compounds. By mismatching the nesting the order can gradually be suppressed and as the Néel temperature tends to zero a quantum critical point is obtained. A superconducting dome above the quantum critical point can be induced by the transfer of pairs of electrons between the pockets. The conditions under which such a dome arises are studied. In addition numerous other phases may arise, e.g. charge density waves, non-Fermi liquid behavior, non-s-wave superconductivity, Pomeranchuk instabilities of the Fermi surface, nematic order, and phases with persistent orbital currents.Schematic phase diagram of the superconducting dome in heavy fermion compounds as function of the tuning parameter δ showing spin-density waves (SDW), a superconducting phase (S+), a mixed phase (SDW+S+), and the crossover region between the non-Fermi liquid (NFL) and Fermi liquid (FL) regions (magenta dashed line). δ0 represents the tuned quantum critical point (QCP). The red curves are first order transitions. PubDate: 2017-11-22T03:00:43.716917-05: DOI: 10.1002/andp.201700263

Authors:Anna Posazhennikova; Mauricio Trujillo-Martinez, Johann Kroha Abstract: If and how an isolated quantum system thermalizes despite its unitary time evolution is a long-standing, open problem of many-body physics. The eigenstate thermalization hypothesis (ETH) postulates that thermalization happens at the level of individual eigenstates of a system's Hamiltonian. However, the ETH requires stringent conditions to be validated, and it does not address how the thermal state is reached dynamically from an initial non-equilibrium state. We consider a Bose-Einstein condensate (BEC) trapped in a double-well potential with an initial population imbalance. We find that the system thermalizes although the initial conditions violate the ETH requirements. We identify three dynamical regimes. After an initial regime of undamped Josephson oscillations, the subsystem of incoherent excitations or quasiparticles (QP) becomes strongly coupled to the BEC subsystem by means of a dynamically generated, parametric resonance. When the energy stored in the QP system reaches its maximum, the number of QPs becomes effectively constant, and the system enters a quasi-hydrodynamic regime where the two subsystems are weakly coupled. In this final regime the BEC acts as a grand-canonical heat reservoir for the QP system (and vice versa), resulting in thermalization. We term this mechanism dynamical bath generation (DBG).How and why does an isolated quantum system come to thermal equilibrium, despite the unitary evolution in quantum mechanics' In this new approach to this well-known problem we show how the system generates its own bath as a result of a parametric resonance at an early stage of a highly nonlinear dynamical process. The evolution to effectively weak system-bath coupling and eventual thermalization is derived microscopically. PubDate: 2017-11-21T06:14:20.682818-05: DOI: 10.1002/andp.201700124

Authors:Chandrachur Chakraborty; Oindrila Ganguly, Parthasarathi Majumdar Abstract: We report an incipient exploration of the Lense-Thirring precession effect in a rotating acoustic analogue black hole spacetime. An exact formula is deduced for the precession frequency of a gyroscope due to inertial frame dragging, close to the ergosphere of a ‘Draining Bathtub’ acoustic spacetime which has been studied extensively for acoustic Hawking radiation of phonons and also for ‘superresonance’. The formula is verified by embedding the two dimensional spatial (acoustic) geometry into a three dimensional one where the similarity with standard Lense-Thirring precession results within a strong gravity framework is well known. Prospects of experimental detection of this new ‘fixed-metric’ effect in acoustic geometries, are briefly discussed.The Lense-Thirring effect due to inertial frame dragging in a rotating spacetime is explored for the first time for a two-dimensional acoustic analogue black hole spacetime known as the ‘Draining Bathtub’. Quantum spin relaxation in interaction with phonons have been known in paramagnetic crystals to induce a spin for phonons which can precess around the orbital angular momentum. This may pave the way for observation of the acoustic analogue of Lense-Thirring precession in a laboratory setup, if realised in a BEC system. PubDate: 2017-11-15T12:31:06.341938-05: DOI: 10.1002/andp.201700231

Authors:Andriy E. Serebryannikov; Akhlesh Lakhtakia, Ekmel Ozbay Abstract: The characteristics of multiple cascaded metasurfaces comprising H-shaped, magnetostatically controllable, subwavelength terahertz (THz) resonators made of InAs were systematically investigated, using a commercial solver based on the finite-integration method, for the design of tunable filters. Three configurations of the biasing magnetostatic field were compared with each other as well as with the bias-free configuration for filtering of normally incident linearly polarized plane waves. A close study of only one metasurface was found sufficient to broadly determine the sensitivity to the direction of the magnetostatic field and the bandwidth of a stopband. Furthermore, the effects of metasurface geometry and biasing field can be considered separately for initial design purposes. All features in the transmittance spectra for the bias-free configuration that are related to the number of cascaded metasurfaces are also observed when the biasing magnetostatic field is applied. The coupling of adjacent metasurfaces in a cascade is strongly affected by the relative permittivity and the thickness of the spacer between the two metasurfaces. The spectral locations of stopbands scale with respect to the spacer's relative permittivity, the scaling rule being different from a classical one. The stopbands are redshifted when the spacer thickness is increased, with the redshift dependent on the polarization of the incident plane wave. Inter-metasurface coupling and inter-resonator coupling on the same metasurface affect the spectral location of a stopband in opposite ways. On-off type switching can be obtained by changing the orientation of magnetostatic field. The elucidated characteristics are expected to be important for not only filters but also other tunable THz devices.Metasurfaces are planar arrays of subwavelength resonators designed to elicit specific performance metrics. Design principles for single and cascaded metasurfaces comprising H-shaped resonators of InAs are extracted from several numerical studies, InAs being a magnetostatically tunable material in the terahertz spectral regime. Magnetostatic biasing, the substrate/spacer material, and resonators on the same and neighboring metasurfaces compete as well as cooperate to deliver tunable stopbands. PubDate: 2017-11-14T12:57:14.530082-05: DOI: 10.1002/andp.201700252

Authors:Wei-Ping Zhong; Milivoj R. Belić, Yiqi Zhang Abstract: By using the modified Snyder-Mitchell (MSM) model, which can describe the propagation of a paraxial beam in fractional dimensions (FDs), we find the exact "accessible soliton” solutions in the strongly nonlocal nonlinear media with a self-consistent parity-time (PT) symmetric complex potential. The exact solutions are constructed with the help of two special functions: the complex Gegenbauer and the generalized Laguerre polynomials in polar coordinates, parametrized by two nonnegative integer indices - the radial and azimuthal mode numbers (n,m), and the beam modulation depth. By the choice of different soliton parameters, the intensity and angular profiles display symmetric and asymmetric structures. We believe that it is important to explore the MSM model in FDs and PT-symmetric potentials, for a better understanding of nonlinear FD physical phenomena. Different physical systems in which the model might be of relevance are briefly discussed.Nonlinear nonlocal systems with PT symmetry and fractional dimension have come to the focus of researchers in various fields of physics. Such systems commonly appear in nonlinear optics, where the change in the refractive index appears as a potential in the Schrȍdinger equation, allowing for optical analogues of various quantum-mechanical phenomena. The authors study fraction-dimensional accessible soliton solutions of the modified Snyder-Mitchell model of strongly nonlocal nonlinear Schrȍdinger equation with a self-consistent PT-symmetric potential. The exact solutions are constructed with the help of Gegenbauer and Laguerre polynomials in polar coordinates, parametrized by two integer indices - the radial and azimuthal mode numbers. By the choice of different parameters, the intensity of solitons displays symmetric and asymmetric structures. PubDate: 2017-11-14T02:37:18.058034-05: DOI: 10.1002/andp.201700311

Authors:Jieci Wang; Jiliang Jing, Heng Fan Abstract: We study the behavior of monogamy deficit and monogamy asymmetry for Einstein-Podolsky-Rosen steering of Gaussian states under the influence of the Hawking effect. We demonstrate that the monogamy of quantum steering shows an extreme scenario in the curved spacetime: the first part of a tripartite system cannot individually steer two other parties, but it can steer the collectivity of the remaining two parties. We also find that the monogamy deficit of Gaussian steering, a quantifier of genuine tripartite steering, are generated due to the influence of the Hawking thermal bath. Our results elucidate the structure of quantum steering in tripartite quantum systems in curved spacetime.The steering monogamy deficit and the steering monogamy asymmetry are defined. The monog-amy of quantum steering shows an extreme scenario in the curved spacetime: the first part of a tripartite system cannot individually steer two other parties, but it can steer the collective of the remaining two parties. The maximizing condition for the monogamy asymmetry is exactly the transition point of the bipartite steering asymmetry. PubDate: 2017-11-14T02:36:42.127999-05: DOI: 10.1002/andp.201700261

Authors:Taiming Sun; Zhixiang Deng, Jiabing Sheng, Zhiyong Chen, Weihua Zhu, Wei Guo, Xinlin Wang Abstract: We studied numerically the enhanced optical transmission (EOT) through periodic subwavelength circular-sharp hole arrays in metallic films with different edge sharp distribution features of unit structures. Detailed studies indicate that the unit structure edge sharp distribution features strongly influence the surface plasmons (SPs). These results demonstrate that the number of edge sharp activated the localized surface plamons (LSP) resonance on the unit structure is changed by rotating the polarization of the incident light, leading to change the infrared transmittance of the array. Moreover, a compact plasmonic switch via periodic circular-sharp hole arrays based on the dependence of SPs on unit structural edge sharp distributions is proposed. The finding provides a new idea for designing plasmonics devices, and expands the application range of metal micro-nano structure in the field of optical communications and information processing.In this study, the enhanced optical transmission (EOT) of circular-sharps shaped hole arrays have been investigated numerically. It is found that the edge sharp distributions have influence the transmission of light mainly by changing the LSP resonance strength on edge sharp. Base on this, a compact plasmonic switch via periodic circular-sharp hole arrays is proposed. It is turned “on” and “off” state by changing the direction of polarization of the light. This research expand the application range of metal micro-nano structure in the field of optical communications and information processing. PubDate: 2017-11-13T06:00:11.938797-05: DOI: 10.1002/andp.201700299

Authors:Patrycja Łydżba; Janusz Jacak Abstract: We introduce a method that allows the disclosure of correlations between particle positions in an arbitrary many-body system. The method is based on a well-known simulated annealing algorithm and the proposed artificial distribution technique. Additionally, we investigate correlations in quantum Hall liquids (we consider many-body wave functions that have been recently determined via the cyclotron subgroup model) and present three-dimensional plots of configuration probability distributions that have been established from numerical simulations. We demonstrate that the preferred simultaneous positions of particles (configurations of positions, which correspond to large values of a system's probability distribution, ΨN 2) tend to form complicated geometric structures, which are equivalent to classical Wigner crystals only for Laughlin states. Furthermore, we claim that quantum Hall liquids attributed to non-Laughlin fillings are correlated on subdomains rather than on a whole particle domain (due to a quantizing magnetic field, which modifies the topology of a system's dynamics). Finally, we characterize Hall-like internal orders in terms of statistical correlations (one-dimensional unitary representations of cyclotron subgroups). Our conclusions concerning the stability of many-body states agree with transport measurements and various numerical studies.A numerical procedure which allows to disclose correlations between particle positions in many-body systems is proposed. It can identify the most probable configuration of wave function’s arguments and the configuration probability distribution. In the paper, the numerical procedure is implemented to describe internal correlations of quantum Hall liquids. Differences between Laughlin and Jain liquids are revealed and explained. Investigated many-body wave functions were deduced from the topological approach. PubDate: 2017-11-13T05:59:41.06973-05:0 DOI: 10.1002/andp.201700221

Authors:Jinjin Jin; Xiaohu Zhang, Ping Gao, Jun Luo, Zuojun Zhang, Xiong Li, Xiaoliang Ma, Mingbo Pu, Xiangang Luo Abstract: Ascribing to the properties of two dimensional parallel focusing and imaging, low propagation loss, integration and miniaturization, microlens array has been widely used in imaging, optical communication, organic light emitting devices, adaptive optics, photolithography, biomedical and other applications. However, the existing traditional microlens array suffers from difficulty in fabrication, large-thickness, curved surface, non-uniformity of light spots, or requirement of additional discrete components to control the microlens. Herein, a planar microlens array is experimentally demonstrated based on the geometric metasurface. The single microlens is composed of space-variant subwavelength metallic gratings with high polarization conversion efficiency and thus exhibits gradient phase distribution. The focused spot diameter of 22.5 μm with radius of 350 μm, focal length of 1 cm and the light spots intensity uniformity of 0.9885 (standard deviation 0.0115) at the focal plane are obtained. Moreover, the broadband property of microlens array is also confirmed. The novel design strategy for microlens array would facilitate the miniaturization of optical devices and be easily integrated in the optical interconnected devices.The microlens array is realized by the ultrathin metasurface, which posses numerous merits including ultrathin (≈λ/10), flat and flexible. Experiment results indicate the uniformity of the focus spots generated by the microlens is high up to 0.9885. This approach may facilitate the applications of the metasurface and advance the high integration of the parallel optical systems. PubDate: 2017-11-13T05:57:27.707631-05: DOI: 10.1002/andp.201700326

Authors:Emanuele Verrelli; Irini Michelakaki, Nikos Boukos, Georgios Kyriakou, Dimitris Tsoukalas Abstract: In this work is presented the growth model for Au films grown on a carbon substrate at room temperature by using as building blocks Au nanoparticles (NPs) with 1.4 nm mean size generated via remote cluster beam synthesis and soft landing on the substrate. The key results highlighted in this work are that 1) the deposited nanoparticles coalesce at substrate level in such a way that the film growth is 3D, 2) newly formed nanoparticles at substrate level are predominantly magic number clusters and 3) coalescensce takes place as soon as two neighboring nanopartciles come closer than a critical distance. The film growth was investigated by TEM as a function of Au load, in the range 0–1.2 μg/cm2. Two distinct regimes are identified: the “landing regime” and the “coalescence regime”. During the latter the film growth is 3D with a dynamic scaling exponent z of 2.13. Particular attention was devoted to the study of the evolution of the NP population from the moment they are generated with the cluster beam generator to the moment they land on the substrate and coalesce with other NPs. Our results show that 1) the NPs generated by the cluster beam are heterogeneous in size and are made by more than 95% by Au Magic numbers, mainly Au20 and Au55 and 2) kinetic processes (coalescence) at substrate level is capable of producing NPs populations made of larger Au magic numbers containing up to several thousands of Au atoms. Experimental and simulation results provide insight into the coalescence mechanism and provide strong evidence that the NPs coalesce when the nearest neighbor distance is below a critical mark. The critical distance is at its minimum 0.4-0.5 nm and it is still unclear whether it is constant or not although the best matching simulation results seem to point to a superlinear dependence from the NP size difference between two neighboring candidate coalescing NPs. The coalescence phenomenon investigated in this work pinpoints the unique self-organization properties of these small Au NPs in creating films with a stable edge-to-edge mean nearest neighbor distance of the order of 1.4 nm.Au films grown by depositing sub-2m Au nanoparticles show that 1) the deposited nanoparticles coalesce at substrate level in such a way that the film growth is 3D, 2) newly formed nanoparticles at substrate level are predominantly magic number clusters and 3) coalescensce takes place as soon as two neighboring nanopartciles come closer than a critical distance. A range of gold magic numbers have been identified, some created directly by the cluster beam generator (e.g. Au55) and others formed through kinetic processes (coalescence) taking place at substrate level upon NP deposition (e.g. Au561). PubDate: 2017-11-13T05:56:59.51565-05:0 DOI: 10.1002/andp.201700256

Authors:Mario Junior Neves; Jose A. Helaÿel-Neto Abstract: The standard electroweak interaction is here re-assessed to accommodate two different situations in Particle Physics. The first one is a Z′-model at the TeV-scale physics. The second one tackles the recent discussion of a possible fifth force mediated by a 17-MeV X-boson associated with an electron-positron emission in the transition of an excited 8-Beryllium to its ground state. The anomaly-free model that provides these two scenarios is based on an SUL(2)×UR(1)J×U(1)K-symmetry. It yields a new massive neutral boson, an exotic massive neutral fermion, right-neutrinos and an additional neutral Higgs particle, which stems from a supplementary Higgs field, introduced along with the usual Higgs doublet responsible for the electroweak breaking and the masses of W± and Z0. Yukawa interactions of the two scalars generate the masses of the Standard Model leptons, neutrinos and a new exotic fermion of the model. The vacuum expectation values of the Higgses fix up two independent energy scales. One of them is the well-confirmed electroweak scale, 246 GeV, whereas the other one is set up by adopting an experimental estimate for the Z′-mass.The model sets out to study an extension of the standard electroweak model with a spontaneous symmetry breaking pattern that yields scenarios with a heavy or a light gauge boson. The introduction of a new exotic fermionic particle, allowed by the symmetries, connects the known barionic matter with a possible dark matter sector through the cascade effects involving the heavy or the light boson decays. The model may be of interest to describe the phenomenology of new particles including also the dark sector in an energy scale above or below the Standard Model scale. PubDate: 2017-11-13T05:55:59.263488-05: DOI: 10.1002/andp.201700112

Authors:Joachim Wosnitza Abstract: In this short review, the recently found experimental evidence that Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) states are realized in quasi-two-dimensional (2D) organic superconductors is reported. At low temperatures and when a high magnetic field is aligned parallel to the conducting organic layers, an upturn of the upper critical field much beyond the Pauli limit is observed, as proven by thermodynamic measurements. Under certain conditions, a second thermodynamic transition emerges inside the FFLO state. Nuclear magnetic resonance (NMR) work has added strong microscopic support for the realization of the FFLO state. The NMR spectra in the FFLO phase can very well be explained by a nonuniform one-dimensionally modulated superconducting order parameter. All these features, appearing only in a very narrow angular region close to parallel-field orientation, give robust evidence for the realization of the FFLO state in organic superconductors.High magnetic fields favor parallel spins, whereas singlet superconducting Cooper pairs have antiparallel spins. As predicted already 1964 by Fulde and Ferrell and, independently, by Larkin and Ovchinnikov, a compromise superconducting state may still exist even beyond the Pauli limit with spatially separated superconducting (orange Cooper pairs) and magnetically ordered regions (blue). Here, the author reviews the clear evidence for these so-called FFLO states found in layered organic superconductors. PubDate: 2017-11-03T01:31:01.324302-05: DOI: 10.1002/andp.201700282

Authors:Tong Cai; Guang-Ming Wang, He-Xiu Xu, Shi-Wei Tang, Haipeng Li, Jian-Gang Liang, Ya-Qiang Zhuang Abstract: Manipulating circularly-polarized (CP) waves in desired multi-prescribed manners, especially in both transmission and reflection schemes, in a single flat device is of particular importance in photonic integration, imaging processing and communication systems. However, available approaches suffer from large thickness, low efficiencies as well as limited wavefront control spaces. Here, we propose a general strategy by using specially tailored Pancharatnam-Berry (PB) meta-atoms with helicity-dependent transmissions and reflections to design high-efficiency CP bifunctional metasurfaces. As a proof of the strategy, two metadevices are designed and characterized at microwave frequencies: the former one achieving focusing/diverging lenses at transmission/reflection side of the metasurface; the latter one realizing CP beam separation under illuminations of CP waves with different chirality, respectively. Both numerical and experimental results demonstrate the predicted EM functionalities, and all these functionalities exhibit very high efficiencies (88%∼94%). Our findings afford a new route to design high-performance CP bi-functional metasurfaces operating in other frequency domains or with other functionalities.Manipulating circularly-polarized (CP) waves in desired multi-prescribed manners, especially in both transmission and reflection schemes, is of particular importance. Here, we propose a general strategy by using specially tailored Pancharatnam-Berry meta-atoms with helicity-dependent transmissions and reflections to design high-efficiency CP bifunctional metasurfaces. As a proof of the strategy, two bifunctional metadevices are designed and characterized at microwave frequencies, and both of them exhibit very high efficiencies (88%∼94%). PubDate: 2017-11-02T04:12:25.64414-05:0 DOI: 10.1002/andp.201700321

Authors:Sk Noor Nabi; Saurabh Basu Abstract: A spinor (F=1) Bose gas is studied in presence of a density-density interaction through a mean field approach and a perturbation theory for either sign of the spin dependent interaction, namely the antiferromagnetic (AF) and the ferromagnetic cases. In the AF case, the charge density wave (CDW) phase appears to be sandwiched between the Mott insulating (MI) and the supersolid phases for small values of the extended interaction strength. But the CDW phase completely occupies the MI lobe when the extended interaction strength is larger than a certain critical value related to the width of the MI lobes and hence opens up the possibilities of spin singlet and nematic CDW insulating phases. In the ferromagnetic case, the phase diagram shows similar features as that of the AF case and are in complete agreement with a spin-0 Bose gas. The perturbation expansion calculations nicely corroborate the mean field phase results in both these cases. Further, we extend our calculations in presence of a harmonic confinement and obtained the momentum distribution profile that is related to the absorption spectra in order to distinguish between different phases.A strong enough long range density-density interaction, in addition to a plethora of interesting phases, replaces the Mott insulating lobes by the charge density wave phases and results in spin density states in the phase diagram of a spin-1 Bose gas. Study of the absorption spectra via the momentum distribution profile in presence of a harmonic confinement yields lucid signatures of the different quantum phases. PubDate: 2017-10-24T06:35:03.506619-05: DOI: 10.1002/andp.201700245

Authors:Haixiang Ma; Xinzhong Li, Yuping Tai, Hehe Li, Jingge Wang, Miaomiao Tang, Jie Tang, Yishan Wang, Zhaogang Nie Abstract: We report on a novel optical vortex array named circular optical vortex array, which is generated by the superposition of two concentric perfect optical vortices. The circular optical vortex array has a constant topological charge of +1 or −1, the number and sign of which are determined by the topological charges of the two perfect optical vortices. Moreover, the radius of the circular optical vortex array is easily adjusted by using the cone angle of an axicon. Furthermore, the circular optical vortex array and multiple circular optical vortex array can be rotated by changing the initial phase difference of the perfect optical vortices on demand. This work demonstrates a complex structured optical field, which is of significance for applications such as optical tweezers, micro-particle manipulation, and optical imaging.This work reports on a novel circular optical vortex array(COVA) generated by the superposition of two concentric perfect vortices. The COVA has a constant topological charge(TC) of ±1, the number and sign of which are determined by the TCs of the perfect vortices. The COVA and multiple COVA can be rotated by changing the initial phase difference. This work is of significance for applications such as optical tweezers and micro-particle manipulation. PubDate: 2017-10-23T03:26:17.711664-05: DOI: 10.1002/andp.201700285

Authors:S. H. Hendi; N. Riazi, S. Panahiyan Abstract: The content of this paper includes studying holographical and thermodynamical aspects of dyonic black holes in the presence of massive gravity. For the first part of paper, thermodynamical properties of the bulk which includes black holes are studied and the main focus is on critical behavior. It will be shown that the existence of massive gravitons introduces remnant for temperature after evaporation of black holes, van der Waals phase transition for non-spherical black holes and etc. The consistency of different thermodynamical approaches toward critical behavior of the black holes is presented and the physical properties near the region of thermal instability are given. Next part of the paper studies holographical aspects of the boundary theory. Magnetization and susceptibility of the boundary are extracted and the conditions for having diamagnetic and paramagnetic behaviors are investigated. It will be shown that generalization to massive gravity results into the existence of diamagnetic/paramagnetic phases in phase structure of the hyperbolic and horizon flat of boundary conformal field theory.Recent LIGO report of detecting the gravitational waves provided a deep insight to general relativity and existence of massive gravitons. Also, phase transition of black holes in analogy to the van der Waals gas/liquid system, opens a new theoretical avenue to study black hole thermodynamics. The effects of graviton's mass on thermodynamical structure of dyonic black holes and holographic properties of the corresponding conformal field theory are explored. PubDate: 2017-10-16T04:26:15.083353-05: DOI: 10.1002/andp.201700211

Authors:Ye-Hong Chen; Qi-Cheng Wu, Bi-Hua Huang, Jie Song, Yan Xia, Shi-Biao Zheng Abstract: It is still a challenge to experimentally realize shortcuts to adiabaticity (STA) for a non-Hermitian quantum system since a non-Hermitian quantum system's counterdiabatic driving Hamiltonian contains some unrealizable auxiliary control fields. In this paper, we relax the strict condition in constructing STA and propose a method to redesign a realizable supplementary Hamiltonian to construct non-Hermitian STA. The redesigned supplementary Hamiltonian can be eithersymmetric or asymmetric. For the sake of clearness, we apply this method to an Allen-Eberly model as an example to verify the validity of the optimized non-Hermitian STA. The numerical simulation demonstrates that a ultrafast population inversion could be realized in a two-level non-Hermitian system.The authors have proposed a method to achieve quantum accelerated dynamics (Shortcuts to adiabaticity) for fast quantum population transfer in non-Hermitian systems. This method is performed by introducing a series of redesigned supplementary Hamiltonians in the original Hamiltonian, which has the purpose to cancel the specified non-adiabatic couplings such that the evolution of the system would be confined in one of the instantaneous eigenstates. PubDate: 2017-10-13T07:05:32.107577-05: DOI: 10.1002/andp.201700247

Authors:Abraão J.S. Capistrano Abstract: In this paper we examine the evolution of cosmic density parameters in a four-dimensional space-time embedded in a five-dimensional bulk space. We show that the extrinsic curvature is an independent spin-2 field governed by the Gupta equations. Without evoking a dark energy fluid, the corresponding cosmological model is compared with the phenomenological XCDM model and shows a good concordance with recent cosmological datasets from Planck Collaboration and the latest Baryons Acoustic Oscillations/Cosmic Microwave Background (BAO/CMBR) + SNIa studying the evolution of density parameters. In addition, a discussion on the coincidence problem is also proposed.In this paper we examine the evolution of cosmic density parameters in a four-dimensional space-time embedded in a five-dimensional bulk space. We show that the extrinsic curvature is an independent spin-2 field governed by the Gupta equations. Without evoking a dark energy fluid, the corresponding cosmological model is compared with the phenomenological XCDM model and shows a good concordance with recent cosmological datasets from Planck Collaboration and the latest Baryons Acoustic Oscillations/Cosmic Microwave Background (BAO/CMBR) + SNIa studying the evolution of density parameters. In addition, a discussion on the coincidence problem is also proposed. PubDate: 2017-10-10T00:31:17.694157-05: DOI: 10.1002/andp.201700232

Authors:Liping Li; Bo Wang, Xin-You Lü, Ying Wu Abstract: This paper will discuss the chaos-related localization in a lattice array with an external periodical field acted on a boundary site that allows us to realize the controllable chaotic dynamics with a tunable driving frequency. Two types of chaos-related localization, short-term and long-term localization, which are closely related to the degree of chaos are reported and may provide a way to realize switching from chaos-related localization to chaos-assisted tunneling. Interestingly, with the increase of nonlinearity, driving frequency or even second-order coupling, there always exists a parameter window with sharp edges for long-term localization which facilitates us to find the thresholds to control the system into or out of localization region. In addition, the numerical results further demonstrate that the initial phase of the driving field may greatly influence the degree of the chaos. These results can be extended to finite driven N-site system and may deepen our understanding of chaos-related localization in nonlinear driving system.Two types of chaos-related localization, short-term localization and long-term localization, are investigated in a driven nonlinear lattice array. The switching from chaos-related localization to chaos-assisted tunneling may realized by adjusting the intensities of nonlinearity, driving frequency, second-order coupling or even the initial driving phase. These results provide a promising route to control the chaotic dynamic and promote the understanding of chaos-related localization. PubDate: 2017-10-10T00:12:15.470578-05: DOI: 10.1002/andp.201700218

Authors:Fabian Kolley; Oriol Bohigas, Boris V. Fine Abstract: We numerically investigate statistical ensembles for the occupations of eigenstates of an isolated quantum system emerging as a result of quantum quenches. The systems investigated are sparse random matrix Hamiltonians and disordered lattices. In the former case, the quench consists of sudden switching-on the off-diagonal elements of the Hamiltonian. In the latter case, it is sudden switching-on of the hopping between adjacent lattice sites. The quench-induced ensembles are compared with the so-called “quantum micro-canonical” (QMC) ensemble describing quantum superpositions with fixed energy expectation values. Our main finding is that quantum quenches with sparse random matrices having one special diagonal element lead to the condensation phenomenon predicted for the QMC ensemble. Away from the QMC condensation regime, the overall agreement with the QMC predictions is only qualitative for both random matrices and disordered lattices but with some cases of a very good quantitative agreement. In the case of disordered lattices, the QMC ensemble can be used to estimate the probability of finding a particle in a localized or delocalized eigenstate.The authors numerically investigate statistical ensembles for the occupations of eigenstates of an isolated quantum system emerging as a result of quantum quenches. The systems investigated are sparse random matrix Hamiltonians and disordered lattices. The quench-induced ensembles are compared with the so-called “quantum micro-canonical” (QMC) ensemble describing quantum superpositions with fixed energy expectation values. We find that quantum quenches with sparse random matrices can lead to the condensation phenomenon predicted for the QMC ensemble. In the case of disordered lattices, the QMC ensemble can be used to estimate the probability of finding a particle in a localized or delocalized eigenstate. PubDate: 2017-10-10T00:12:03.710913-05: DOI: 10.1002/andp.201700009

Authors:Luciano Combi; Gustavo E. Romero Abstract: An axiomatization of the so-called Teleparallel Equivalent to General Relativity is presented. A set of formal and semantic postulates are elaborated from where the physical meaning of various key concepts of the theory are clarified. These concepts include those of inertia, Lorentz and diffeomorphism invariance, and reference frame. It is shown that Teleparallel Gravity admits a wider representation of space-time than General Relativity, allowing to define properties of the gravitational field such as energy and momentum that are usually considered problematic. In this sense, although the dynamical equations of both theories are equivalent, their inequivalence from a physical point of view is demonstrated. Finally, the axiomatic formulation is used to compare Teleparallel Gravity with other theories of gravity based on absolute parallelism such as non-local and f(T) gravity.Teleparallel Gravity is an alternative formulation of General Relativity with equivalent field equations and a different dynamical object. This object, a tetrad field, encodes a broader interpretation than the metric since it also represents the reference frame. Together with the Weitzenböck geometry, Teleparallel Gravity presents additional features which cannot be obtained in General Relativity. The authors show that a strict equivalence between both theories cannot be established applying an axiomatic method. PubDate: 2017-10-09T06:12:25.900793-05: DOI: 10.1002/andp.201700175

Authors:Jianji Yang; David Sell, Jonathan A. Fan Abstract: Conventional phased-array metasurfaces utilize subwavelength-scale nanoparticles or nanowaveguides to specify spatially-dependent amplitude and phase responses to light. An alternative design strategy is based on freeform inverse optimization, in which wavelength-scale elements are designed to produce devices that possess exceptionally high efficiencies. In this report, we theoretically analyze the physical mechanisms enabling high efficiency in freeform-based periodic metasurfaces, i.e., metagratings. An in-depth coupled mode analysis of ultra-wide-angle beam deflectors and wavelength splitters shows that the extraordinary performance of these designs originates from the large number of propagating modes supported by the metagrating, in combination with complex multiple scattering dynamics exhibited by these modes. We also apply our coupled mode analysis to conventional nanowaveguide-based metagratings to understand and quantify the factors limiting the efficiencies of these devices. We envision that freeform metasurface design methods will open new avenues towards high-performance, multi-functional optics by utilizing strongly coupled nanophotonic modes and elements.Conventional optical metasurfaces utilize sub-λ nanoscatterers to specify spatially-dependent amplitude and phase responses. An alternative design strategy is based on freeform inverse optimization, where wavelength-scale elements are designed to produce devices that possess ultra-high efficiencies. The mechanisms of high-efficiency freeform metasurfaces are analyzed here. A coupled mode analysis shows that the extraordinary performance of these designs originates from the large number of propagating modes and their complex multiple scattering dynamics. PubDate: 2017-10-09T06:11:39.510438-05: DOI: 10.1002/andp.201700302

Authors:Moumita Das; Biswajit Sen, Ayan Ray, Anirban Pathak Abstract: Possibilities of generation of lower order and higher order intermodal entanglement in four-wave mixing (FWM) process are rigorously investigated using Sen-Mandal perturbative technique. The investigation has revealed that for a set of experimentally realizable parameters, one can observe lower order and higher order intermodal entanglement between pump and signal modes and signal and idler modes in a FWM process. In addition, trimodal entanglement involving pump, signal and idler modes is also reported.Possibilities of generation of lower order and higher order intermodal entanglement in four-wave mixing (FWM) process are rigorously investigated using Sen-Mandal perturbative technique. The investigation has revealed that for a set of experimentally realizable parameters, one can observe lower order and higher order intermodal entanglement between pump and signal modes and signal and idler modes in a FWM process. In addition, trimodal entanglement involving pump, signal and idler modes is also reported. PubDate: 2017-09-27T09:47:30.976672-05: DOI: 10.1002/andp.201700160

Authors:Bernhard Stanje; Daniel Rettenwander, Stefan Breuer, Marlena Uitz, Stefan Berendts, Martin Lerch, Reinhard Uecker, Günther Redhammer, Ilie Hanzu, Martin Wilkening Abstract: The development of all-solid-state electrochemical energy storage systems, such as lithium-ion batteries with solid electrolytes, requires stable, electronically insulating compounds with exceptionally high ionic conductivities. Considering ceramic oxides, garnet-type Li7La3Zr2O12 and derivatives, see Zr-exchanged Li6La3ZrTaO12 (LLZTO), have attracted great attention due to its high Li+ ionic conductivity of 10−3 S cm−1 at ambient temperature. Despite numerous studies focussing on conductivities of powder samples, only few use time-domain NMR methods to probe Li ion diffusion parameters in single crystals. Here we report on temperature-variable NMR relaxometry measurements using both laboratory and spin-lock techniques to probe Li jump rates covering a dynamic time window spanning several decades. Both techniques revealed a consistent picture of correlated Li ion jump diffusion in the single crystal; the data perfectly mirror a modified BPP-type relaxation response being based on a Lorentzian-shaped relaxation function. The rates measured could be parameterized with a single set of diffusion parameters. Results from NMR are completely in line with ion transport parameters derived from conductivity spectroscopy.The Li ions in single crystals of Li6La3ZrTaO12 are exposed to fast very fast exchange processes. The reason behind these fast hopping processes, which have been revealed by NMR spin-lattice relaxometry, is an enhanced pre-factor of the underlying Arrhenius relation that boosts ion dynamics above room temperature. The pre-factor is, besides other factors, influenced by entropic contributions. PubDate: 2017-09-13T01:08:55.999298-05: DOI: 10.1002/andp.201700140

Authors:Carlos Ramírez Abstract: Calculation of the scattering matrix (S-matrix) of a system allows direct determination of its transport properties. Within the scattering theory, S-matrices relate amplitudes of incoming and outgoing waves in semi-infinite leads attached to a scattering region. Recently, an assembly method to calculate S-matrices of arbitrary tight-binding systems connected to atomic chains has been proposed, were the S-matrices of subsystems are used to obtain S-matrix of the total system. In this paper, a new efficient method to obtain S-matrices of general periodic leads is established, which can be used in the mentioned assembly method, allowing to address coherent quantum transport of arbitrary multiterminal systems with complex geometries trough Landauer-Büttiker formalism. In addition, a new method to determine extended-state band structures of general infinite periodic wires is presented, which exploits properties of the S-matrix. Finally, these methods are used to obtain band structure of graphene arm-chair and zig-zag nanoribbons and transmission functions in three terminal Z-shaped graphene nanoribbon structures.In this work, a new method to determine the S-matrix of semi-infinite periodic tight-binding systems is described. This method is compatible with an assembly process that allow determination of transport properties of complex systems by using simpler elements. Transmission functions of Z-shape graphene systems with arm-chair and zig-zag leads, as shown in figure, are determined as instances of application. PubDate: 2017-09-13T01:07:39.593601-05: DOI: 10.1002/andp.201700170

Authors:Maxim F. Gelin; Raffaele Borrelli Abstract: We develop a wave-function-based method for the simulation of quantum dynamics of systems with many degrees of freedom at finite temperature. The method is inspired by the ideas of Thermo Field Dynamics (TFD). As TFD, our method is based on the doubling of the system's degrees of freedom and thermal Bogoliubov transformation. As distinct from TFD, our method implements the doubling of thermalized degrees of freedom only, and relies upon the explicitly constructed generalized thermal Bogoliubov transformation, which is not restricted to fermionic and bosonic degrees of freedom. This renders the present approach computationally efficient and applicable to a large variety of systems.The authors develop a wave-function-based method for the simulation of quantum dynamics of systems with many degrees of freedom at finite temperature.The method is inspired by the ideas of Thermo Field Dynamics. It implements the doubling of thermalized degrees of freedom and relies upon the explicitly constructed thermal Bogoliubov transformation, which is not restricted to fermionic and bosonic degrees of freedom. PubDate: 2017-09-06T01:51:03.322141-05: DOI: 10.1002/andp.201700200

Authors:Evgueni Talantsev; Wayne P. Crump, Jeffery L. Tallon Abstract: Key questions for any superconductor include: what is its maximum dissipation-free electrical current (its ‘critical current') and can this be used to extract fundamental thermodynamic parameters' Present models focus on depinning of magnetic vortices and implicate materials engineering to maximise pinning performance. But recently we showed that the self-field critical current for thin films is a universal property, independent of microstructure, controlled only by the penetration depth. Here, using an extended BCS-like model, we calculate the penetration depth from the temperature dependence of the superconducting energy gap thus allowing us to fit self-field critical current data. In this way we extract from the T-dependent gap a set of key thermodynamic parameters, the ground-state penetration depth, energy gap and jump in electronic specific heat. Our fits to 79 available data sets, from zinc nanowires to compressed sulphur hydride with critical temperatures of 0.65 to 203 K, respectively, are excellent and the extracted parameters agree well with reported bulk values. Samples include thin films, wires or nanowires of single- or multi-band s-wave and d-wave superconductors of either type I or type II. For multiband or multiphase samples we accurately recover individual band contributions and phase fractions.Self-field critical current data for many different superconductors is fitted by calculating the London penetration depth from the temperature dependence of the superconducting energy gap. This allows key thermodynamic parameters to be determined including the jump in electronic specific heat. Fits to 79 data sets, from zinc nanowires to compressed sulphur hydride with Tc from 0.65 to 203 K, respectively, are excellent and extracted parameters agree well with reported values. PubDate: 2017-09-06T01:41:25.007695-05: DOI: 10.1002/andp.201700197

Authors:Evaldas Stankevičius; Mantas Garliauskas, Mindaugas Gedvilas, Nikolai Tarasenko, Gediminas Račiukaitis Abstract: Here, the structuring of surfaces with gold nanoparticles by using Bessel-like beam array is demonstrated. The experimental results show that the fabricated microring structures containing gold nanoparticles have a surface plasmon resonance in the spectral range of 520–540 nm, which can be tuned by selecting the laser treatment parameters. Fabricated microring structures exhibit a lower light transmittance comparing with the randomly distributed gold nanoparticles for wavelengths 500–570 nm due to the growth in the size of nanoparticles. In the spectral range of 600–700 nm, the light transmittance through microring structures is higher compared with the randomly distributed gold nanoparticles because of the removal of gold nanoparticles as gold has high reflectivity for wavelengths longer than 600 nm. The demonstrated method enables an easy fabrication of microring structures having tunable plasmonic properties.Fabrication of multi-ring structures consisting of gold nanoparticles is presented. Ring structures of gold nanoparticles with micron scale widths and millimeter scale lengths can induce localized surface plasmon resonance. The localized surface plasmon resonance coupling possessed by the ring-typed structure can significantly enhance fluorescence intensities and surface enhanced Raman spectroscopy signals. Furthermore, fabricated structures may find broad applications in near-field imaging, sensing, lithography and nanoparticle manipulations. PubDate: 2017-09-05T11:57:57.665729-05: DOI: 10.1002/andp.201700174

Authors:Borzoo Nazari Abstract: The energy of the massless scalar field inside parallel Casimir plates in a general weak gravitational field under the influence of Robin boundary conditions is calculated. The mode frequencies are found in asymptotic limits and consistency of results with the literature is shown. Experimental evidence for detection of corrections is explored.The Casimir effect is a famous quantum field theoretical phenomenon under external boundary conditions. We study the influence of a general gravitational field on the Casimir plates for Robin boundary conditions. The induced corrections on mode frequencies and energy inside the plates can be used to put constraints on the local behavior of the modified gravitational theories. PubDate: 2017-09-05T11:55:42.797605-05: DOI: 10.1002/andp.201700142

Authors:Michele Merano Abstract: A classical theory of a radiating two-dimensional crystal is proposed and an expression for the radiation-reaction electric field is derived. This field plays an essential role in connecting the microscopic electromagnetic fields acting on each dipole of the crystal to the macroscopic one, via the boundary conditions for the system. The expression of the radiative-reaction electric field coincides with the macroscopic electric field radiating from the crystal and, summed to the incident electric field, generates the total macroscopic electric field.As for a three-dimensional solid, a local electromagnetic field acts on each atom or molecule in a two-dimensional crystal. Thus, the question that arises is how to go from the microscopic description to the macroscopic one. Surprisingly these two descriptions are connected via the radiative-reaction electric field felt by each microscopic constituent. PubDate: 2017-09-05T11:55:33.015045-05: DOI: 10.1002/andp.201700062

Authors:Xiaohu Zhang; Mingbo Pu, Jinjin Jin, Xiong Li, Ping Gao, Xiaoliang Ma, Changtao Wang, Xiangang Luo Abstract: The photonic spin-orbit interaction (PSOI) in inhomogeneous anisotropic metasurface has drawn much attentions recently due to its superior ability to manipulate light wave in the deep-subwavelength scale. Traditional methods involving PSOI are limited to operational spectral bandwidth owing to the intrinsic dispersion of the constitutive materials. In this paper, a helicity-multiplexing scheme is proposed to achieve independent control of the PSOI in both the spectral and spatial domains by combining the broadband characteristic with polarization dependence of the metasurface. Two simultaneous functions of multicolor holographic display and polarization encryption are experimentally demonstrated with a single metasurface perforated with nanoholes. Although the optical response of the nanoholes themselves are almost independent of the light wavelength, the obtained image can have abundant spectral information. The approach proposed here is promising for realizing multifunction optical device, multicolor display, optical storage and information encryption.A helicity multiplexed scheme is proposed by combining the broadband characteristic with polarization dependence of the anisotropic metasurface consisted of elongated nanoapertures. Two different functions, the multicolor holographic display and polarization encryption, are experimentally demonstrated simultaneously by a single metasurface. The proposed method has enormous potential applications in multicolor display, multifunction device and encryption technology etc. PubDate: 2017-09-04T08:26:05.970351-05: DOI: 10.1002/andp.201700248

Authors:Stefan Meinecke; Benjamin Lingnau, André Röhm, Kathy Lüdge Abstract: Simultaneous two-state lasing is a unique property of semiconductor quantum-dot (QD) lasers. This not only changes steady-state characteristics of the laser device but also its dynamic response to perturbations. In this paper we investigate the dynamic stability of QD lasers in an external optical injection setup. Compared to conventional single-state laser devices, we find a strong suppression of dynamical instabilities in two-state lasers. Furthermore, depending on the frequency and intensity of the injected light, pronounced areas of bistability between both lasing frequencies appear, which can be employed for fast optical switching in all-optical photonic computing applications. These results emphasize the suitability of QD semiconductor lasers in future integrated optoelectronic systems where a high level of stability is required.Semiconductor lasers with quantum-dots as active material are able to simultaneously lase at two wavelength. They can be exploited for all-optical switching applications, if implemented in an optical injection setup. We analyse the stability properties and discuss the parameter dependence of the bi-stability regions between ground-state (GS) and excited-state (ES) emission. Interestingly, a large tolerance to optical perturbations is found for these two-state lasers. PubDate: 2017-08-28T04:57:02.685952-05: DOI: 10.1002/andp.201600279

Authors:Felix Schwarz; Erich Runge Abstract: The potential of disorder to confine and enhance electromagnetic fields is well known and localized fields in turn can be used for non-linear optical sensing and for studying quantum optics. Recently, nanoporous gold nanoparticles (nanosponges) were shown to support highly localized long-lived plasmonic modes in the infrared spectral range. In this paper, we take first steps towards tailoring the disorder for optimal field localization and enhancement by calculating extinction and near-field properties for different filling fractions and correlation lengths. We find that the filling fraction has not only a large effect on the fundamental dipolar surface-plasmon resonance of the nanoparticle, but also on the frequency range in which localized modes of plasmonic nature occur. The influence of the correlation length is more subtle but is seen to influence the coupling between localized and far-field modes as well. We briefly discuss first results on details of the localization process, which takes place on the same length scale as the typical structure size, so a simple cavity-resonance picture cannot account for the relatively low frequency of the modes.Nanoporous gold nanoparticles (nanosponges) intrinsically confine and enhance electromagnetic fields as plasmonic modes on a length scale given by the pore size, which is well below optical wavelengths. This opens new routes towards, e.g., non-linear optical sensing and nano-scale quantum optics. A numerical study varies filling fractions and feature size of the gold sponges in order to understand and optimize the presence of long-lived ultra-localized plasmonic modes. PubDate: 2017-08-23T12:26:58.284084-05: DOI: 10.1002/andp.201600234

Authors:Stefan G. Fischer; Clemens Gneiting, Andreas Buchleitner Abstract: We systematically derive the semiclassical limit of a charged particle's motion in the presence of an infinitely long and infinitesimally thin solenoid carrying magnetic flux. Our limit establishes the connection of the particle's quantum mechanical canonical angular momentum to the latter's classical counterpart. A picture of Aharonov-Bohm interference of two half-waves acquiring Dirac's magnetic phase when passing on either side of the solenoid naturally emerges from the quantum propagator. The resulting interference pattern is fully determined by the ratio of the angular part of Hamilton's principal function to Planck's constant, and the wave interference smoothes out discontinuities in the semiclassical propagator which is recovered in the limit when the above ratio diverges. We discuss the relation of our results to the whirling-wave representation of the exact propagator, and to previous approaches on the system's asymptotics.A novel derivation of the semiclassical limit is presented for a particle propagating in the presence of an Aharonov-Bohm vector potential. The derivation shows how the quantum mechanical canonical angular momentum is transformed into the latter's classical counterpart, and a characteristic half-wave interference pattern naturally emerges in an intermediate stage of the limiting procedure. PubDate: 2017-08-14T02:05:50.105018-05: DOI: 10.1002/andp.201700120

Authors:Massimiliano Di Ventra; Fabio L. Traversa, Igor V. Ovchinnikov Abstract: It is well known that dynamical systems may be employed as computing machines. However, not all dynamical systems offer particular advantages compared to the standard paradigm of computation, in regard to efficiency and scalability. Recently, it was suggested that a new type of machines, named digital –hence scalable– memcomputing machines (DMMs), that employ non-linear dynamical systems with memory, can solve complex Boolean problems efficiently. This result was derived using functional analysis without, however, providing a clear understanding of which physical features make DMMs such an efficient computational tool. Here, we show, using recently proposed topological field theory of dynamical systems, that the solution search by DMMs is a composite instanton. This process effectively breaks the topological supersymmetry common to all dynamical systems, including DMMs. The emergent long-range order – a collective dynamical behavior– allows logic gates of the machines to correlate arbitrarily far away from each other, despite their non-quantum character. We exemplify these results with the solution of prime factorization, but the conclusions generalize to DMMs applied to any other Boolean problem.Digital memcomputing machines are dynamical systems that can solve complex problems efficiently. Their computational power originates from a transient instantonic phase that creates non-locality in the system. The instantons connect topologically inequivalent critical points in the phase space as shown in the schematic. PubDate: 2017-08-07T01:40:48.153723-05: DOI: 10.1002/andp.201700123