摘要
通过调节短程相互作用,在Su-Schrieffer-Heeger(SSH)模型中实现了Dirac点的移动与融合.该过程对应于一种由半金属相到能带绝缘相的拓扑相变(即Lifshitz相变).通过解析和数值研究的方法,对该相变过程中系统准粒子的相对论动力学特性进行了研究.结果表明:在短程相互作用很弱的情况下(即Dirac点融合前),系统展现出相对论动力学特征;然而,随着短程相互作用的增强,Dirac点会发生融合相变.此后,系统则表现为非相对论动力学特征.因此,相变过程是由相对论到非相对论动力学转变的过程.进一步通过数值模拟得到了融合前(相对论)后(非相对论)粒子的密度分布随时间演化的图像.在相变前,单色Dirac准粒子发生劈裂,而双色Dirac准粒子产生定向漂移现象.在相变后,无论初态如何改变,系统始终无组分劈裂现象出现.最后,展示了不同相互作用下准粒子的质心运动曲线(世界线).
The movement and merging of Dirac points were realized in the Su-Schrieffer-Heeger(SSH)model by adjusting short-range interaction.This process corresponded to a topological phase transition from a semi-metallic to a band insulating phase,known as Lifshitz phase transition.The dynamical properties of relativistic quasi-particles in this process were investigated with the analytical and numerical methods.The system exhibited relativistic dynamics under the condition of weak short-range interaction(i.e.,before the merging of Dirac points).However,with the increase of the short-range interaction,the merging of Dirac points occurred.After that the system showed non-relativistic dynamics.Therefore,the phase transition was also a transition from relativistic to nonrelativistic dynamics.Furthermore,through numerical simulation,a vivid evolution of quasi-particles'density distribution versus time was presented before(relativistic)and after(non-relativistic)the merging transition.The results reveal that before the phase transition the monochromatic Dirac quasi-particles split while the bi-chromatic Dirac quasi-particles directionally drift.Furthermore,after the phase transition,no matter how the initial state changes,no component splitting occurs in the system.Finally,the centroid motion curves(worldlines)of quasi-particles under different interaction conditions are provided.
作者
李志
胡玥
郭政鑫
陈李梅
黄育蕾
LI Zhi;HU Yue;GUO Zhengxin;CHEN Limei;HUANG Yulei(School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510006, China)
出处
《华南师范大学学报（自然科学版）》
CAS
北大核心
2020年第4期26-30,共5页
Journal of South China Normal University(Natural Science Edition)
基金
国家自然科学基金项目(11704132)
中国博士后科学基金面上项目(2018M633063)。
