六角晶格中Dirac准粒子的动力学模拟与操控

Simulation and Manipulation of Dirac Quasiparticles’ Dynamics in a Hexagonal Lattice

基于装载在六角可调光晶格中的超冷原子气体,研究了无质量狄拉克准粒子的动力学行为.此系统具有与石墨烯类似的能带结构,即在简并点附近满足线性色散关系.分别运用解析求解海森堡运动方程和数值波包动力学的方法,得到了准粒子质心位置.文中可视化地展示了准粒子在不同宽度能隙处的演化行为,发现准粒子的运动并没有出现相对论Zitterbewegung现象.此外,研究了有效光速、Dirac旋量对系统动力学演化的影响.结果表明:波包的演化方式取决于初态Dirac旋子的形式,而运动速度只依赖于有效光速.由于光晶格超冷原子系统具有纯净和高可操控性等优点,文中研究成果有望在超冷原子体系实验中得到验证.

The dynamical properties of massless Dirac quasiparticles are studied with ultracold atomic gases in a tunable hexagonal lattice. The spectrum of the quasiparticles is similar to that of graphene,which undergoes a linear dispersion relationship around the degenerate point. The center of mass of the quasiparticles is obtained with the analytical and numerical methods respectively. The visualized evolution of the quasiparticles shows that the effective energy gap cannot result in Zitterbewegung. Furthermore,the key factors of the wavepacket dynamics,such as effective speed of light and initial Dirac spinors,are also investigated. The result reveals that the evolution of the wave packet of the quasiparticles is dependent on the initial Dirac spinors and the speed of their movement is dependent on the effective speed of light. Because of the purity and high tenability of the ultracold atomic system,the observation of the interesting phenomenon predicted here is expectable in the relevant experiments.