arXiv subjects

Chun-Yang Wang

Publications and source records attributed to Chun-Yang Wang.

At least 19 recordsLinked to original sources

arXiv2021

Phase diagrams, quantum correlations and critical phenomena of antiferromagnetic Heisenberg model on diamond-type hierarchical lattices

The spin-1/2 antiferromagnetic Heisenberg systems are studied on three typical diamond-type hierarchical lattices (systems A, B and C) with fractal dimensions 1.63, 2 and 2.58, respectively, and the phase diagrams, critical phenomena and quantum correlations are calculated by a combination of the equivalent transformation and real-space renormalization group methods. We find that there exist a reentrant behavior for system A and a finite temperature transition in the isotropic Heisenberg limit for system C (not for system B). Unlike the ferromagnetic case, the Neel temperatures of antiferromagnetic systems A and B are inversely proportional to ln(Delta_c-Delta) (when Delta->Delta_c) and ln Delta (when Delta->0), respectively. And we also find that there is a turning point of quantum correlation in the isotropic Heisenberg limit Delta=0 where there is a peak of the contour and no matter how large the size of system is, quantum correlation will change to zero in the Ising limit for the three systems. The quantum correlation decreases with the increase of lattice size L and it is almost zero when L>=30 for system A, and for systems B and C, they still exist when L is larger than that of system A. Moreover, as an example, we discuss the error of result in system A, which is induced by the noncommutativity.

cond-mat.stat-mech↗

arXiv2021

Single-ion anisotropy effects on the critical behaviors of quantum entanglement and correlation in the spin-1 Heisenberg chain

Quantum entanglement and correlations in the spin-1 Heisenberg chain with single-ion anisotropy are investigated using the quantum renormalization group method. Negativity and quantum discord (QD) are calculated with various anisotropy parameters $\bigtriangleup$ and single-ion anisotropy parameters $D$. We focus on the relations between two abovementioned physical quantities and on transitions between the Néel, Haldane, and Large-D phases. It is found that both negativity and QD exhibit step-like patterns in different phases as the size of the system increases. Interestingly, the single-ion anisotropy parameter $D$, which can be modulated using nuclear electric resonance (2020 \textit{Nature} \textbf{579} 205), plays an important role in tuning the quantum phase transition (QPT) of the system. Both the first partial derivative of the negativity and quantum discord with respect to $D$ or $\bigtriangleup$ exhibit nonanalytic behavior at the phase transition points, which corresponds directly to the divergence of the correlation length. The quantum correlation critical exponents derived from negativity and QD are equal, and are the reciprocal of the correlation length exponent at each critical point. This work extends the application of quantum entanglement and correlations as tools for depicting QPTs in spin-1 systems.

cond-mat.str-el↗

arXiv2021

Quantum Quench dynamics in XY spin chain with ferromagnetic and antiferromagnetic interactions

In this manuscript we investigate the one-dimensional anisotropic XY model with ferromagnetic and antiferromagnetic interactions, which gives more interesting phase diagrams and dynamic critical behaviors. By using quantum renormalization-group method, we find that there are three phases in the system: antiferromagnetic Ising phase ordered in "x direction", spin-fluid phase and ferromagnetic Ising phase ordered in "y direction". In order to study the dynamical critical behaviors of the system, two quantum quenching methods are used. In both cases, the concurrence, a measure of entanglement, oscillates periodically over time. We show that the periods are the same and can be used as a new order parameter for quantum phase transitions. For further discussion, we derive the scaling exponent, θ, and correlation length exponent, ν, from the scaling behavior of the evolution period.

cond-mat.stat-mech↗

arXiv2018

Broken mirror symmetry tuned topological transport in PbTe/SnTe heterostructures

The tunability of topological surface states and controllable opening of the Dirac gap are of great importance to the application of topological materials. In topological crystalline insulators (TCIs), crystal symmetry and topology of electronic bands intertwine to create topological surface states and thus the Dirac gap can be modulated by symmetry breaking structural changes of lattice. By transport measurement on heterostructures composed of p-type topological crystalline insulator SnTe and n-type conventional semiconductor PbTe, here we show a giant linear magnetoresistance (up to 2150% under 14 T at 2 K) induced by the Dirac Fermions at the PbTe/SnTe interface. In contrast, PbTe/SnTe samples grown at elevated temperature exhibit a cubic-to-rhombohedral structural phase transition of SnTe lattice below 100 K and weak antilocalization effect. Such distinctive magneto-resistance behavior is attributed to the broken mirror symmetry and gapping of topological surface states. Our work provides a promising application for future magneto-electronics and spintronics based on TCI heterostructures.

cond-mat.mtrl-sci↗

arXiv2015

Structured noise induced non-recross barrier escaping

The time-dependent barrier passage of a particle driven by the structured noise is studied in the field of a metastable potential. Quantities such as the probability of passing over the saddle point and transmission coefficient of the escaping rate are calculated for a thimbleful of insight into the diffusion dynamical properties. Results show that the barrier recrossing behavior is greatly reduced by the structured noisy environment. Particles diffusion in such an dissipative environment tends to successfully escape from the potential well without any embarrassments.

physics.chem-ph↗

arXiv2015

Kramers-type effective Reactive Flow in Structured-noise Environments

The non-Markovian features of three typical anomalous diffusing systems are studied by analytically solving the generalized Langevin equation directly driven by three kind of internal structured-noises: harmonic noise, harmonic velocity noise and harmonic acceleration noise, respectively. The time-dependent reaction rate and the transmission coefficient are calculated by using of the reactive flux method. A startling behavior of Kramers-type effective reactive flow is witnessed in the harmonic noise and harmonic acceleration noise systems.

math.ST↗

arXiv2015

Fractional Non-Markovian effect and Newton's 2nd law of motion

We report in this paper a thorough study on the the dynamical mechanics of the fractional Brownian motion systems. Where several non-trivial properties are revealed such as the abundant non-Markovian effects resulted from the fractional characters of the system. In general, the dynamics of the fBm system is found to be of a purely Newton's type, despite of the anomalous fractional properties of the system.

cond-mat.stat-mech↗

arXiv2015

Fractionally diffusing passing through the saddle point of metastable potential

The diffusion of a fractional Brownian particle passing over the saddle point is studied in the field of the metastable potential. The barrier escaping probability is found to be greatly related to the fractional exponent $α$. Properties are revealed to move reversely in the opposite direction of diffusion when $α$ is relatively large despite of the zero-approximating effective friction of the system. This is very anomalous to the standard Brownian motion.

cond-mat.stat-mech↗

arXiv2015

Fractional extension of Kramers rate and barrier escaping from metastable potential well

The reactive process of barrier escaping from the metastable potential well is studied together with the extension of Kramers' rate formula to the fractional case. Characteristic quantities are computed for an thimbleful of insight into the near barrier escaping and recrossing dynamics. Where the stationary transmission coefficient is revealed to be larger than the usual cases which implies less barrier recrossing. And the non-monotonic varying of it reveals a close dependence to the fractional exponent $α$. In most cases, the near barrier behavior of the escaping dynamics is equivalent to the diffusion in the two-dimensional non-Ohmic damping system.

physics.chem-ph↗

arXiv2013

Fractional Entropy Decaying and the Third Law of Thermodynamics

The quantum thermodynamic property of the fractional damping system is investigated extensively. A fractional power-law decaying entropy function is revealed which presents another evidence for the validity of the third law of thermodynamics in the quantum dissipative region. Several non-trivial characters are excavated such as that the entropy varies from a non-linear diverging function to a semi-linear decaying function of the fractional exponent as the temperature tends to absolute zero.

cond-mat.stat-mech↗

arXiv2012

Time-dependent barrier passage in External Noise Modulated System-reservoir Environment

The time-dependent barrier passage of an anomalous system-reservoir coupling non-equilibrium open environment is studied where the heat bath is modulated by an external noise. The time-dependent barrier passing probability is obtained analytically by solving the generalized Langevin equation. The escaping rate and effective transmission coefficient are calculated by using of the reactive flux method in the particular case of external $δ$-correlated noise modulated internal Ornstein-Uhlenbeck process. It is found that not all the cases of external noise modulating is harmful to the rate process. Sometimes it is even beneficial to the diffusion of the particle. There exists an optimal strength of external noise modulation for the particle to obtain a biggest probability to escape from the potential well to form a notable rate of effective net flux.

physics.chem-ph↗

arXiv2012

Internal and External Fluctuation Activated Non-equilibrium Reactive Rate Process

The activated rate process for non-equilibrium open systems is studied taking into account both internal and external noise fluctuations in a unified way. The probability of a particle diffusing passing over the saddle point and the rate constant together with the effective transmission coefficient are calculated via the method of reactive flux. We find that the complexity of internal noise is always harmful to the diffusion of particles. However the external modulation may be beneficial to the rate process.

physics.chem-ph↗

arXiv2012

Critical Properties of $S^{4}$ System Restudied via Generalized Migdal-Kadanoff Bond-moving Renormalization

We study the critical properties of the spin-continuous $S^{4}$ system on the typical translational invariant triangular lattices by combining the recently-developed generalized Migdal-Kadanoff bond-moving recursion procedures with the cumulative expansion technique. In three different cases of nearest-neighbor, next nearest neighbor and external field we obtain the critical points and further calculate the critical exponents according to the scaling theory. In all case it is found that there exists three fixed points. The correlation length critical exponents obtained near the Wilson-Fisher fixed points are found getting smaller and smaller with the increasing of the system complexity. Others are found similar to the results of the classical Gaussian model and different from those of the Ising system.

math.ST↗

arXiv2011

Generalized Migdal-Kadanoff Bond-moving Renormalization Recursion Procedure I: Symmetrical Half-length Bond Operation on Translational Invariant Lattices

We report in a series of papers two types of generalized Migdal-Kadanoff bond-moving renormalization group transformation recursion procedures. In this first part the symmetrical operation of half length bonds on translational invariant lattices are considered. As an illustration of their predominance in application, the procedures are used to study the critical behavior of the spin-continuous Gaussian model constructed on the triangular lattices. Results such as the correlation length critical exponents obtained by this means are found to be in good conformity with the classical results from other studies.

cond-mat.stat-mech↗

arXiv2011

Generalized Migdal-Kadanoff Bond-moving Renormalization Recursion Procedure II: Symmetrical Half-length Bond Operation on Fractals

In this second part of the series of two papers we report another type of generalized Migdal-Kadanoff bond-moving renormalization group transformation recursion procedures considering symmetrical single bond operations on fractals. The critical behavior of the spin-continuous Gaussian model constructed on the Sierpinski gaskets is studied as an example to reveal its predominance in application. Results obtained by this means are found to be in good conformity with those obtained from other studies.

cond-mat.stat-mech↗

arXiv2011

Entropy and Its Quantum Thermodynamical Implication for Anomalous Spectral Systems

The state function entropy and its quantum thermodynamical implication for two typical dissipative systems with anomalous spectral densities are studied by investigating on their low-temperature quantum behavior. In all cases it is found that the entropy decays quickly and vanishes as the temperature approaches zero. This reveals a good conformity with the third law of thermodynamics and provides another evidence for the validity of fundamental thermodynamical laws in the quantum dissipative region.

cond-mat.stat-mech↗

arXiv2010

Combined Influence of Off-diagonal System Tensors and Potential Valley Returning of the Optimal Path

The two-dimensional barrier passage is studied in the framework of Langevin statistical reactive dynamics. The optimal incident angle for a particle diffusing in the dissipative non-orthogonal environment with various strengths of coupling between the two degrees of freedom is systematically calculated. The optimal diffusion path of the particle in a non-Ohmic damping system is revealed to have a probability to return to the potential valley under the combined influence of the off-diagonal system tensors.

nucl-th↗

arXiv2009

Time-dependent barrier passage of Two-dimensional non-Ohmic damping system

The time-dependent barrier passage of an anomalous damping system is studied via the generalized Langevin equation (GLE) with non-Ohmic memory damping friction tensor and corresponding thermal colored noise tensor describing a particle passing over the saddle point of a two-dimensional quadratic potential energy surface. The time-dependent passing probability and transmission coefficient are analytically obtained by using of the reactive flux method. The long memory aspect of friction is revealed to originate a non-monotonic $δ$(power exponent of the friction) dependence of the passing probability, the optimal incident angle of the particle and the steady anomalous transmission coefficient. In the long time limit a bigger steady transmission coefficient is obtained which means less barrier recrossing than the one-dimensional case.

cond-mat.stat-mech↗