Floquet scattering through a parity–time symmetric oscillating potential

We investigate the scattering of a particle from a trapping potential that is subjected to weak,parity–time symmetric periodic drivings.Using the Floquet theory,we derive the scattering matrix and calculate the transmittance of the incident particle.When the driving is purely coherent,our calculation recovers the known result and the transmission spectrum shows the familiar,bound-state-induced Fano resonances.When the driving is purely incoherent,we find the Fano resonances still occur,but the lineshape of each resonance is reversed compared to the coherent-driving counterpart.Intriguingly,the transmission resonances disappear when both the coherent and incoherent driving fields are present with equal amplitudes.This phenomena can be seen as a manifestation of the non-reciprocal coupling of Floquet channels in the frequency domain.Notably,when the frequency up-conversion is absent,the transmission is such as if there is no driving at all,even when the driving strength increases.

Dimensional crossover of a Rabi-coupled two-component Bose–Einstein condensate in an optical lattice

Dimensionality is a central concept in developing the theory of low-dimensional physics.However,previous research on dimensional crossover in the context of a Bose-Einstein condensate(BEC)has focused on the single-component BEC.To our best knowledge,further consideration of the two-component internal degrees of freedom on the effects of dimensional crossover is still lacking.In this work,we are motivated to investigate the dimensional crossover in a three-dimensional(3D)Rabi-coupled two-component BEC.The spin degrees of freedom consist of the Rabi-like and inter-and intra-interaction coupling constants.The dimensional crossovers from 3D to 2D or 1D are controlled by the continuous increase of 1D or 2D lattice depth respectively.Then we analyze how the dimensionality of the model system combined with spin degrees of freedom can affect quantum fluctuations.Accordingly,the analytical expressions of the ground-state energy and quantum depletion of the system are obtained.Our results show that the dimensional crossover induces a characteristic 3D to quasi-2D or 1D crossover in the behavior of quantum fluctuations,with an emphasis on the separated effects of Rabi-like and inter-and intra-interaction coupling constants on the quantum fluctuations.Conditions for possible experimental realization of our scenario are also discussed.

Hierarchical dimensional crossover of an optically-trapped quantum gas with disorder

Dimensionality serves as an indispensable ingredient in any attempt to formulate low-dimensional physics,and studying the dimensional crossover at a fundamental level is challenging.The purpose of this work is to study the hierarchical dimensional crossovers,namely the crossover from three dimensions(3D)to quasi-2D and then to 1D.Our system consists of a 3D Bose–Einstein condensate trapped in an anisotropic 2D optical lattice characterized by the lattice depths V1 along the x direction and V2 along the y direction,respectively,where the hierarchical dimensional crossover is controlled via V1 and V2.We analytically derive the ground-state energy,quantum depletion and the superfluid density of the system.Our results demonstrate the 3D-quasi-2D-1D dimensional crossovers in the behavior of quantum fluctuations.Conditions for possible experimental realization of our scenario are also discussed.