Bloch Oscillation Of Spin-orbit-coupled Cold Atoms In An Optical Lattice

The cold atom system provides an important sample for the study of quantum system.Benefit from the experiment achievement of Bose-Einstein condensation and the higher tunability of optical lattice,people can study many condensed matter and solid physics in the optical-atom system.We study the Bloch oscillation dynamics of a spin-orbit-coupled cold atomic gas trapped inside a one dimensional optical lattice.If a microscopic particle is subjected to a constant external force in a periodic potential field,it will oscillate periodically.This phenomenon is called Bloch oscillation.We form an optical lattice through a standing wave light field and use cold atoms imprisoned in the optical lattice to simulate electrons moving in the lattice potential field.Spin-orbit coupling is also an important physical phenomenon.We can achieve spin-orbit coupling by coupling the internal hyperfine structure of an atom with the external momentum.On this basis we will study Bloch oscillations of spin-orbit coupled cold atoms.The eigenspectra of the system is identified as two interpenetrating Wannier-Stark ladders.Based on that,we found out that intraladder coupling between neighboring rungs of the Wannier-Stark ladder give rise to ordinary Bloch oscillation,while interladder coupling leads to small-amplitude high-frequency oscillation superimposed on it.Specifically,spin-orbit interaction breaks Galilean invariance,which can be reflected by out-of-phase oscillation of the two spin components in the accelerated frame.The phenomenon of the emergence and disappearance of the spin flow alternating with the time evolution of the system is studied.The innovation of this work is to use the Wannier-Stark ladder to study the dynamics of spin orbit coupling and Bloch oscillations in cold atomic systems,and on this basis to study spin flow generated by spin orbit coupling and chiral Bloch oscillations.