Phase Transition Point Research Articles

Non-Hermitian pseudo-gaps

The notion of a band gap is ubiquitous in the characterization of matter. Particularly interesting are pseudo-gaps, which are enigmatic regions of very low density of states that have been linked to novel phenomena like high temperature superconductivity. In this work, we discover a novel origin for pseudo-gaps when boundaries are introduced in a non-Hermitian lattice. It generically occurs due to the interference between two or more asymmetric pumping channels, and possess no analog in Hermitian systems. Mathematically, it can be visualized as being created by divergences of spectral flow in the complex energy plane, analogous to how sharp edges creates divergent electric fields near an electrical conductor. A non-Hermitian pseudo-gap can host symmetry-protected mid-gap modes like ordinary topological gaps, but the mid-gap modes are extended instead of edge-localized, and exhibit extreme sensitivity to symmetry-breaking perturbations. Surprisingly, pseudo-gaps can also host an integer number of edge modes even though the pseudo-bands possess fractional topological windings, or even no well-defined Chern number at all, in the marginal case of a phase transition point. Challenging conventional notions of topological bulk-boundary correspondences and even the very concept of a band, pseudo-gaps post profound implications that extend to many-body settings, such as fractional Chern insulators.

Enhanced nonlinear quantum metrology with weakly coupled solitons in the presence of particle losses

The estimation of physical parameters with Heisenberg sensitivity and beyond is one of the crucial problems for current quantum metrology. However, unavoidable lossy effect is commonly believed to be the main obstacle when applying fragile quantum states. To utilize the lossy quantum metrology, we offer an interferometric procedure for phase parameters estimation at the Heisenberg (up to 1/N) and super-Heisenberg (up to 1/N^3) scaling levels in the framework of the linear and nonlinear metrology approaches, respectively. The heart of our setup is the novel soliton Josephson Junction (SJJ) system providing the formation of the quantum probe, i.e, the entangled Fock (N00N-like) state, beyond the superfluid-Mott insulator quantum phase transition point. We illustrate that such states are close to the optimal ones even with moderate losses. The enhancement of phase estimation accuracy remains feasible both for the linear and nonlinear metrologies with the SJJs, and allows further improvement for the current experiments performed with atomic condensate solitons with a mesoscopic number of particles.

Universal order-parameter and quantum phase transition for two-dimensional q-state quantum Potts model

We investigate quantum phase transitions for q-state quantum Potts models (q = 2,3,4) on a square lattice and for the Ising model on a honeycomb lattice by using the infinite projected entangled-pair state algorithm with a simplified updating scheme. We extend the universal order parameter to a two-dimensional lattice system, which allows us to explore quantum phase transitions with symmetry-broken order for any translation-invariant quantum lattice system of the symmetry group G. The universal order parameter is zero in the symmetric phase, and it ranges from zero to unity in the symmetry-broken phase. The ground-state fidelity per lattice site is computed, and a pinch point is identified on the fidelity surface near the critical point. The results offer another example highlighting the connection between (i) critical points for a quantum many-body system undergoing a quantum phase-transition and (ii) pinch points on a fidelity surface. In addition, we discuss three quantum coherence measures: the quantum Jensen–Shannon divergence, the relative entropy of coherence, and the l1 norm of coherence, which are singular at the critical point, thereby identifying quantum phase transitions.

Development and precise determination of high reproducibility Ga-In eutectic temperature fixed point

In this paper, the experimental results for binary alloys of gallium with indium melting plateau realization are reported. The Ga-In eutectic plateaus can last for more than 80 h with a temperature change of less than 1.5 mK. Various methods were employed to accurately determine the phase transition point of the Ga-In eutectic. By calculation, the point of inflection (POI) manner shows the best performance and is recommended for the determination of the Ga-In eutectic phase transition point. By repeatedly realising Ga-In eutectic melting plateaus, the melting point temperature was determined to be 15.6479 °C, with a reproducibility of less than 0.14 mK. The corresponding realization uncertainty of Ga-In eutectic was also analyzed and was found to be 0.90 mK (k = 2). These results are consistent with those of previous studies within the associated uncertainties and will help better understand the phase diagram and the corresponding thermal properties of the Ga-In eutectic.

Elucidation of optical, thermal, morphological and antimicrobial efficacy of L-tryptophan hydrochloride single crystals

An efficient semi-organic nonlinear optical single crystal of L-tryptophan hydrochloride (LTHC) of molecular formula C11H13N2O2Cl has been synthesized and its elemental composition was confirmed by EDS analysis. The crystallographic system and lattice parameters were found by single crystal XRD analysis which indicates the synthesized crystal corresponds to monoclinic system of space group P21 and its crystalline nature was identified by powder XRD analysis. The typical characteristic vibrational modes of the grown LTHC crystal were identified by FTIR spectral analysis. The grown crystal’s optical properties were analyzed by UV-Vis-NIR and Photoluminescence analyses. The wavelength dependent optical constants were also measured, and its refractive index at 532 nm was found to be 1.67. The grown crystal’s mechanical stability was determined with the help of Vicker’s hardness tester, which revealed that LTHC has soft material behaviour. TG-DTA-DSC tests were used to examine the thermal behaviour such as decomposition phenomena, phase transition, and melting point of the grown crystal, which revealed that it has high thermal stability up to 205 degrees. The dielectric behaviour, a.c. conductivity of LTHC crystal was studied by dielectric studies and its nonlinear efficiency was analyzed by Kurtz-Perry technique. The crystalline morphology of LTHC was examined by TEM and SEM analyses. Its optical damage property was analyzed by laser damage threshold analysis. The antimicrobial property of LTHC was also scrutinized against bacterial as well as fungal strains by Agar disk diffusion method. Finally, all these findings recommended that LTHC crystals could be useful in biomedical and nonlinear optics applications.

Nonlinear electrodynamics effects on the black hole shadow, deflection angle, quasinormal modes and greybody factors

In this paper, we discuss the effects of nonlinear electrodynamics (NED) on non-rotating black holes, parametrized by the field coupling parameter β and magnetic charge parameter P in detail. Particularly, we survey a large range of observables and physical properties of the magnetically charged black hole, including the thermodynamic properties, observational appearance, quasinormal modes and absorption cross sections. Initially, we show that the NED black hole is always surrounded by an event horizon and any magnetic charge is permissible. We then show that the black hole gets colder with increasing charge. Investigating the heat capacity, we see that the black hole is thermally stable between points of phase transition. Introducing a generalized uncertainty principle (GUP) with a quantum gravity parameter λ extends the range of the stable region, but the effect on temperature is negligible. Then we compute the deflection angle at the weak field limit, by the Gauss-Bonnet theorem and the geodesic equation, and find that even at the first order, the magnetic charge has a contribution due to the “field mass” term. Small changes of the charge contributes greatly to the paths of null geodesics due to the P 2 dependence of the horizon radius. Using a ray-tracing code, we simulate the observational appearance of a NED black hole under different emission profiles, thin disk and spherical accretion. We find that the parameter P has a very strong effect on the observed shadow radius, in agreement with the deflection angle calculations. We finally consider quasinormal modes under massless scalar perturbations of the black hole and the greybody factor. We find that the charge introduces a slight difference in the fundamental frequency of the emitted waveform. We find that the greybody factor of the NED black hole is strongly steepened by the introduction of increasing charge. To present observational constrains, we show that the magnetic charge of the M87* black hole is between 0 ≤ P ≤ 0.024 in units of M, in agreement with the idea that real astrophysical black holes are mostly neutral. We also find that LIGO/VIRGO and LISA could detect NED black hole perturbations from BHs with masses between 5 M ☉ and 8.0 · 108 M ☉. We finally show that for black holes with masses detected with LIGO so far, charged NED black holes would deviate from Schwarzschild by 5∼10 Hz in their fundamental frequencies.

Electrical circuit simulation of nonreciprocal Aubry-André models

<sec>The introduction of non-Hermiticity into traditional Hermitian quantum systems generalizes their basic notions and brings about many novel phenomena, e.g., the non-Hermitian skin effect that is exclusive to non-Hermitian systems, attracting enormous attention from almost all branches of physics. Contrary to the quantum platforms, classical systems have the advantages of low cost and mature techniques under room temperature. Among them, the classical electrical circuits are more flexible on simulating quantum tight-binding models in principle with any range of hopping under any boundary conditions in any dimension, and have become a powerful platform for the simulation of quantum matters. In this paper, by constructing an electrical circuit, we simulate by SPICE the static properties of a prototypical non-Hermitian model—the nonreciprocal Aubry-André (AA) model that has the nonreciprocal hopping and on-site quasiperiodic potentials. </sec><sec>The paper is organized as follows: Following the introduction, in Sec. II we review in detail the Laplacian formalism of electrical circuits and the mapping to the quantum tight-binding model. Then, in Sec. III, an electrical circuit is proposed with resistors, capacitors, inductors, and the negative impedance converters with current inversion (INICs), establishing a mapping between the circuit's Laplacian and the non-reciprocal AA model's Hamiltonian under periodic boundary conditions (PBCs) or open boundary conditions (OBCs). Especially, the nonreciprocity, the key of this model, is realized by INICs. In Sec IV, based on the mapping, for the proposed circuit under PBCs, we reconstruct the circuit's Laplacian via SPICE by measuring voltage responses of an AC current input at each node. The complex spectrum and its winding number <inline-formula><tex-math id="M1">\begin{document}$\nu$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220219_M1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220219_M1.png"/></alternatives></inline-formula> can be calculated by the measured Laplacian, which are consistent with the theoretical prediction, showing <inline-formula><tex-math id="M2">\begin{document}$\nu=\pm 1$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220219_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220219_M2.png"/></alternatives></inline-formula> for non-Hermitian topological regimes with complex eigenenergies and extended eigenstates, and <inline-formula><tex-math id="M3">\begin{document}$\nu=0$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220219_M3.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="16-20220219_M3.png"/></alternatives></inline-formula> for topologically trivial regimes with real eigenenergies and localized eigenstates. In Sec V, for the circuit under OBCs, a similar method is used for measuring the node distribution of voltage response, which simulates the competition of non-Hermitian skin effects and the Anderson localization, depending on the strength of quasiperiodic potentials; the phase transition points also appear in the inverse participation ratios of voltage responses. </sec><sec>During the design process, the parameters of auxiliary resistors and capacitors are evaluated for obtaining stable responses, because the complex eigenfrequecies of the circuits are inevitable under PBCs. Our detailed scheme can directly instruct further potential experiments, and the designing method of the electrical circuit is universal and can in principle be applied to the simulation for other quantum tight-binding models. </sec>

High-order exceptional point in a quantum system of two qubits with interaction

<sec>As one of the essential features in non-Hermitian systems coupled with environment, the exceptional point has attracted much attention in many physical fields. The phenomena that eigenvalues and eigenvectors of the system simultaneously coalesce at the exceptional point are also one of the important properties to distinguish from Hermitian systems. In non-Hermitian systems with parity-time reversal symmetry, the eigenvalues can be continuously adjusted in parameter space from all real spectra to pairs of complex-conjugate values by crossing the phase transition from the parity-time reversal symmetry preserving phase to the broken phase. The phase transition point is called an exceptional point of the system, which occurs in company with the spontaneous symmetry broken and many novel physical phenomena, such as sensitivity-enhanced measurement and loss induced transparency or lasing. Here, we focus on a two-qubit quantum system with parity-time reversal symmetry and construct an experimental scheme, prove and verify the features at its third-order exceptional point, including high-order energy response induced by perturbation and the coalescence of eigenvectors.</sec><sec>We first theoretically study a two-qubit non-Hermitian system with parity-time reversal symmetry, calculate the properties of eigenvalues and eigenvectors, and prove the existence of a third-order exceptional point. Then, in order to study the energy response of the system induced by perturbation, we introduce an Ising-type interaction as perturbation and quantitatively demonstrate the response of eigenvalues. In logarithmic coordinates, three of the eigenvalues are indeed in the cubic root relationship with perturbation strength, while the fourth one is a linear function. Moreover, we study the eigenvectors around exceptional point and show the coalescence phenomenon as the perturbation strength becomes smaller.</sec><sec>The characterization of the response of eigenvalues at high-order exceptional points is a quite difficult task as it is in general difficult to directly measure eigenenergies in a quantum system composed of a few qubits. In practice, the time evolution of occupation on a particular state is used to indirectly fit the eigenvalues. In order to make the fitting of experimental data more reliable, we want to determine an accurate enough expressions for the eigenvalues and eigenstates. To this aim, we employ a perturbation treatment and show good agreement with the numerical results of states occupation obtained by direct evolution. Moreover, we find that after the system evolves for a long enough time, it will end up to one of the eigenstates, which gives us a way to demonstrate eigenvector coalescence by measuring the density matrix via tomography and parity-time reversal transformation.</sec><sec>To show our scheme is experimentally applicable, we propose an implementation using trapped <inline-formula><tex-math id="M2">\begin{document}$ ^{171} {\rm{Yb}}^{+}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220716_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="13-20220716_M2.png"/></alternatives></inline-formula> ions. We can map the parity-time reversal symmetric Hamiltonian to a purely dissipative two-ion system: use microwave to achieve spin state inversion, shine a 370 nm laser to realize dissipation of spin-up state, and apply Raman operation for Mølmer-Sørensen gates to implement Ising interaction. By adjusting the corresponding microwave and laser intensity, the spin coupling strength, the dissipation rate and the perturbation strength can be well controlled. We can record the probability distribution of the four product states of the two ions and measure the density matrix by detecting the fluorescence of each ion on different Pauli basis.</sec>

Temperature dependence of dielectric permittivity in incommensurately modulated phase of ammonium fluoroberyllate

We study the temperature dependence of dielectric permittivity along the polar axis for ferroelectric ammonium fluoroberyllate (AFB) crystal in the vicinity of its phase transition points. The experimental data within incommensurately modulated phase of AFB is compared with the predictions of phenomenological models known from the literature: the Curie-Weiss (CW) law, the generalized Curie-Weiss (GCW) law, and the models by Levanyuk and Sannikov (LS) and by Prelovšek, Levstik and Filipič (PLF) suggested for improper ferroelectrics. It is shown that the LS approach describes the temperature behavior of the dielectric permittivity for the AFB crystal better than the CW, GWC and PLF models. The main physical reasons of this situation are elucidated.

The Phase Transition of Calcium Sulfide Under High Pressure

We carried out the accurate in situ angle derisive x-ray diffraction experiments and the electrical resistivity in CaS under high pressure. The result shows the pressure-induced phase transition of CaS from Na Cl-type structure (the space group Fm3m, phase I ) to Cs Cl-type structure (the space group Pm3m, phase II ) is reversible and the transition point is around 40.0 GPa; in the meantime, the electrical resistivity and light permeability decrease as the pressure increases and occur obvious discontinuities at the corresponding phase transition point; the result of the first-principles calculations is in concordance with the measurement results.

High-order exceptional point in a quantum system of two qubits with interaction

As one of the essential features in non-Hermitian systems coupled with environment, the exceptional point has attracted much attention in many physical fields. The phenomena that eigenvalues and eigenvectors of the system simultaneously coalesce at the exceptional point are also one of the important properties to distinguish from Hermitian systems. In non-Hermitian systems with parity-time reversal symmetry, the eigenvalues can be continuously adjusted in parameter space from all real spectra to pairs of complex-conjugate values by crossing the phase transition from the parity-time reversal symmetry preserving phase to the broken phase. The phase transition point is called an exceptional point of the system, which occurs in company with the spontaneous symmetry broken and many novel physical phenomena, such as sensitivity-enhanced measurement and loss induced transparency or lasing. Here, we focus on a two-qubit quantum system with parity-time reversal symmetry and construct an experimental scheme, prove and verify the features at its third-order exceptional point, including high-order energy response induced by perturbation and the coalescence of eigenvectors.<br/>We first theoretically study a two-qubit non-Hermitian system with parity-time reversal symmetry, calculate the properties of eigenvalues and eigenvectors, and prove the existence of a third-order exceptional point. Then, in order to study the energy response of the system induced by perturbation, we introduce an Ising-type interaction as perturbation and quantitatively demonstrate the response of eigenvalues. In logarithmic coordinates, three of the eigenvalues are indeed in the cubic root relationship with perturbation strength, while the fourth one is a linear function. Moreover, we study the eigenvectors around exceptional point and show the coalescence phenomenon as the perturbation strength becomes smaller.<br/>The characterization of the response of eigenvalues at high-order exceptional points is a quite diffcult task as it is in gneneral diffcult to directly measure eigenenergies in a quantum system composed of a few qubits. In practice, the time evolution of occupation on a particular state is used to indirectly fit the eigenvalues. In order to make the fitting of experimental data more reliable, we want to determine an accurate enough expressions for the eigenvalues and eigenstates. To this aim, we employ a perturbation treatment and show good agreement with the numerical results of states occupation obtained by direct evolution. Moreover, we find that after the system evolves for a long enough time, it will end up to one of the eigenstates, which gives us a way to demonstrate eigenvector coalescence by measuring the density matrix via tomography and parity-time reversal transformation.<br/>To show our scheme is experimentally applicable, we propose an implementation using trapped <sup>171</sup>Yb+ ions. We can map the parity-time reversal symmetric Hamiltonian to a purely dissipative two-ion system:use microwave to achieve spin state inversion, shine a 370 nm laser to realize dissipation of spin-up state, and apply Raman operation for Mølmer-Sørensen gates to implement Ising interaction. By adjusting the corresponding microwave and laser intensity, the spin coupling strength, the dissipation rate and the perturbation strength can be well controlled. We can record the probability distribution of the four product states of the two ions and measure the density matrix by detecting the fluorescence of each ion on different Pauli basis.

Dielectric Measurements of Nanocrystalline VO-=SUB=-2-=/SUB=- : Fe Films

Dielectric spectroscopy methods revealed the existence of two types of relaxation processes in the semiconductor phase of VO2 : Fe films. The characteristic relaxation times are denoted by tau1 and tau2. It is shown that the temperature dependences of tau1 and tau2 have hysteresis, the position of the loops of which coincides with the points of the semiconductor-metal phase transition. in VO2 : Fe films. tau1 corresponds to undoped, and tau2 corresponds to Fe-doped nanocrystallites of the VO2 film. It is shown that the physical mechanism of the relaxation process is due to the establishment of equilibrium after the action of an electric field on conduction electrons. The numerical values of the parameters of the distribution of relaxers over relaxation times are determined. Keywords: dielectric measurements, correlation effects, vanadium dioxide, VO2, insulator-metal phase transition

Диэлектрические измерения нанокристаллических пленок VO-=SUB=-2-=/SUB=- : Fe

Dielectric spectroscopy methods revealed the existence of two types of relaxation processes in the semiconductor phase of VO2:Fe films. The characteristic relaxation times are denoted by τ1 and τ2. It is shown that the temperature dependences of τ1 and τ2 have hysteresis, the position of the loops of which coincides with the points of the semiconductor-metal phase transition. in VO2:Fe films. τ1 corresponds to undoped, and τ2 corresponds to Fe-doped nanocrystallites of the VO2 film. It is shown that the physical mechanism of the relaxation process is due to the establishment of equilibrium after the action of an electric field on conduction electrons. The numerical values of the parameters of the distribution of relaxers over relaxation times are determined.

Исследование водородной дилатации мембран на основе переходных металлов

Niobium absorbs hydrogen well, which is accompanied by structural and phase changes in the metal. To study the phenomenon of "hydrogen embrittlement" in niobium, the work presents studies of the dilatation of samples of pure niobium and palladium-coated niobium foil at different pressures in a gaseous medium. Hydrogen dilatation measurements were carried out on a setup developed based on a Shimadzu AG 100kNx electromechanical testing machine. A series of experiments to study the deformation of niobium membranes was carried out in two stages. At the first stage, pure niobium samples were studied; at the second stage, niobium samples palliated on both sides were studied. An oxide film on the surface of niobium significantly reduces the rate of diffusion of hydrogen atoms into the bulk of the sample, which leads to the development of slow dilatation in niobium in a hydrogen atmosphere. The deposition of a catalytic palladium film on the niobium surface provides a hundreds-fold increase in the flow rate of hydrogen atoms into the sample volume. It has been proved that it is advantageous for hydrogen to occupy tetrahedral positions in the niobium lattice. To study the strain rate and detect points of phase transitions, isobars for niobium and tantalum were plotted. Based on the isobar analysis, the linear thermal expansion coefficient of Nb and Ta was calculated. A rearrangement of the crystal lattice of the base metal in the region of high temperatures, accompanied by a change in the symmetry of the structure of the substance, has been found.

Discovering formation of ice 0 by low-frequency measurement data

In this work, low-frequency characteristics of wetted nanoporous silicate materials were measured, as well as the specimen’s own low-frequency electric fluctuations at the frequencies of 1…100 Hz. The measurements at low frequencies were conducted at different voltages of the probing signal. A capacity cell was used in making the measurements. In the experiments, at the temperatures below –25…–30 °C, non-linearity of the medium was discovered. The experiments on the study of the specimen’s own electric fluctuations at these temperatures revealed their essential increase. These temperatures are below the point of phase transition of supercooled water to recently discovered ferroelectric ice 0. Based on the measurements made, a conclusion was made regarding formation of this modification of ice in the nanosize pores of the wetted materials under study. Ice 0 is a ferroelectric; therefore, its formation from deeply supercooled water may have a significant impact on the electric parameters of wetted bodies at the temperatures below –23 °C. At the interface of such ice with another dielectric, a thin layer with practically metallic conductivity emerges. Such a layer influences not only the non-linear dependence of dielectric permittivity on the electric field but also increases attenuation of electromagnetic radiation in a medium.

Stable solitons and their controllability in <inline-formula><tex-math id="M2">\begin{document}$ {\cal{PT}}$\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20220475_M2.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20220475_M2.png"/></alternatives></inline-formula> symmetrical polariton condensates

By constructing the spatial distribution of external potential and incoherent pumping, a <inline-formula><tex-math id="M8">\begin{document}$ {\cal{PT}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20220475_M8.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20220475_M8.png"/></alternatives></inline-formula> symmetrical model satisfied by the one-dimensional incoherent pumped exciton-polariton condensate system is designed. In the weakly nonlinear case, the <inline-formula><tex-math id="M9">\begin{document}$ {\cal{PT}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20220475_M9.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20220475_M9.png"/></alternatives></inline-formula> symmetrical phase transition point is found, and the linear spectrum is shown. In the normal nonlinear case, found are the bright soliton with the zero background, the multi-poles dark solitons with zero background, the symmetry breaking dark solitons and symmetrical dark soliton with the homogeneous background, and the dip- and hump-type dark solitons with the homogeneous background, and discussed are the effects of inhomogeneous pumping and the imaginary part of external potential on the profiles and the stability of solitons. Through these results, the competition between <inline-formula><tex-math id="M10">\begin{document}$ {\cal{PT}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20220475_M10.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20220475_M10.png"/></alternatives></inline-formula> symmetrical potential and the inhomogeneous pumping is understood, the scheme that how the bright and dark solitons are excited is presented, and the existence and stability regions of these solitons are determined. Finally, the symmetry breaking dark solitons are controlled by modulating the imaginary part of the <inline-formula><tex-math id="M11">\begin{document}$ {\cal{PT}} $\end{document}</tex-math><alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20220475_M11.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="18-20220475_M11.png"/></alternatives></inline-formula> symmetrical potential, which reveals the potential applications of the polariton condensate system in optical information processing, such as the all-optical switches.

Природа фазовых переходов. (Роль самосогласованной обратной связи в эволюции материальных структур)

The inability of statistical mechanics to determine the bounds of the condensed media phase regions, to compute the thermodynamic coordinates of phase transitions, to predict the molecular structures astride of the phase transition points, to estimate the rates of transitions from nonequilibrium to equilibrium, to determine the dependence of the solid body structure on the rate of the liquid melt cooling, etc. , is one of the most chronic diseases of modern theory. All these defects are related to the fundamental problem of unification of the laws acting in microcosm and in macrocosm. It is indisputable that these laws describe the same, i.e. , material systems of many interacting particles. Therefore, a general law must exist which connects both the levels of description of matter into a comprehensive whole. Mechanics itself does not contain the collective properties of many-particle systems, but, following the general logic, the signature of these properties should take place in the laws which govern the microscopic behavior of the system elements. The feedback principle pretends to accomplish such unification without any violation of the principles which underlie statistical mechanics.

Quantum batteries at the verge of a phase transition

Starting from the observation that the reduced state of a system strongly coupled to a bath is, in general, an athermal state, we introduce and study a cyclic battery–charger quantum device that is in thermal equilibrium, or in a ground state, during the charge storing stage. The cycle has four stages: the equilibrium storage stage is interrupted by disconnecting the battery from the charger, then work is extracted from the battery, and then the battery is reconnected with the charger; finally, the system is brought back to equilibrium. At no point during the cycle are the battery–charger correlations artificially erased. We study the case where the battery and charger together comprise a spin-1/2 Ising chain, and show that the main characteristics—the extracted energy and the thermodynamic efficiency—can be enhanced by operating the cycle close to the quantum phase transition point. When the battery is just a single spin, we find that the output work and efficiency show a scaling behavior at criticality and derive the corresponding critical exponents. Due to always present correlations between the battery and the charger, operations that are equivalent from the perspective of the battery can entail different energetic costs for switching the battery–charger coupling. This happens only when the coupling term does not commute with the battery’s bare Hamiltonian, and we use this purely quantum leverage to further optimize the performance of the device.

MULTIFUNCTIONAL CrxCa(10-x)Al30Si60 GLASSES, ELECTRICAL CONDUCTIVITY AND THERMOLUMINESCENCE

The SiO2 glasses embedded with Cr3+ ions are notable for solid state optical resource, which are useful in various opto-electronic and semiconducting applications. However, the available thermoluminescent resource, which include different electronic and semiconducting materials, need some refinement in their structure, luminescence, and electronic properties towards development of advanced glass resource. In this vision, CrxCa(10-x)Al30Si60 glassy materials have planned for synthesis and testing. The GT, and GC phase transition points, and thermal stability (~1.2639) of test samples are identified. Structural vibrations are identified with the help of FT-IR spectra. The order of electrical conductivity (~1.657x10-4 ohm-1 cm-1), and A.E. (~0.3669 eV) of test samples reveal their electrical strength. The symmetry (~ 0.576%) factor, frequency (1.1172 X 1020 S -1) factor, and A.E. (0.682 eV) of the test samples are recorded under 30 kGy irradiation. Overall, the results, which include structure, electrical and luminescence of the test samples suggest the materials might be useful electrically conductive and thermal stimulated light resource.

Influence of mesoporous size and structure on heat transport characteristics of mixed nitrate

The effects of mesoporous size and structure on the solidification characteristics of solar salt are simulated by molecular dynamics (MD). The mixed nitrate model with different scales and two structures is established by using Material Studio software, and the model is applied to the Lammps software package for simulation calculation. The changes of freezing point, supercooling, and phase transformation latent heat are summarized. The micro mechanism of solidification characteristics of nano solar salt is analyzed by radial distribution function, potential energy temperature curve and Gibbs free energy theory. The results show that the freezing point of solar salt first increases and then decreases with the increase of nanopore scale. The nanowire structure will also increase the phase transition temperature on the same scale, and the phase transition points of the two eventually tend to be stable with the increase of scale. The supercooling of solar salt decreases with the increase of mesoporous scale, but there is an abnormal increase. Under the two different structures, the solidification enthalpy gradually decreases with the increase of scale, and the phase transition latent heat of nanowire solar salt is 30%–37% higher than that of nanoparticle structure on the same scale.