Quench dynamics of ultracold atoms in one-dimensional optical lattices with artificial gauge fields

We study the quench dynamics of noninteracting ultracold atoms loaded in one-dimensional （1D） optical lattices with artificial gauge fields, which are modeled by lattices with complex hopping coefficients. After suddenly changing the hopping coefficient, time evolutions of the density distribution, momentum distribution, and mass current at the center are studied for both finite uniform systems and trapped systems. Effects of filling factor, system size, statistics, harmonic trap, and phase difference in hopping are identified, and some interesting phenomena show up. For example, for a finite uniform fermionic system shock and rarefaction wave plateaus are formed at two ends, whose wave fronts move linearly with speed equaling to the maximal absolute group velocity. While for a finite uniform bosonic system the whole density distribution moves linearly at the group velocity. Only in a finite uniform fermionic system there can be a constant quasi- steady-state current, whose amplitude is decided by the phase difference and filling factor. The quench dynamics can be tested in ultracold atoms with minimal modifications of available experimental techniques, and it is a very interesting and fundamental example of the transport phenomena and the nonequilibrium dynamics.

A new form of Tsallis distribution based on the probabilistically independent postulate

The current form of Tsallis distribution for a Hamiltonian system with an arbitrary potential is found to represent a simple isothermal situation. This paper finds that the q-exponential of a sum can be applied as the product of the q- exponential based on the probabilistically independent postulate employed in nonextensive statistical mechanics. Under this framework, a new form of Tsallis distribution is suggested. It shows that the new form of Tsallis distribution can supply the statistical description for the nonequilibrium dynamical property of the Hamiltonian system governed by an arbitrary potential, and it is found to be one potential statistical distribution for the dark matter.

Microcavity exciton polaritons at room temperature

The quest for realizing novel fundamental physical effects and practical applications in ambient conditions has led to tremendous interest in microcavity exciton polaritons working in the strong coupling regime at room temperature.In the past few decades,a wide range of novel semiconductor systems supporting robust exciton polaritons have emerged,which has led to the realization of various fascinating phenomena and practical applications.This paper aims to review recent theoretical and experimental developments of exciton polaritons operating at room temperature,and includes a comprehensive theoretical background,descriptions of intriguing phenomena observed in various physical systems,as well as accounts of optoelectronic applications.Specifically,an in-depth review of physical systems achieving room temperature exciton polaritons will be presented,including the early development of ZnO and GaN microcavities and other emerging systems such as organics,halide perovskite semiconductors,carbon nanotubes,and transition metal dichalcogenides.Finally,a perspective of outlooking future developments will be elaborated.