本学期第六次午餐会将于下周二12月5日中午举行，由北京师范大学物理学系刘海文研究员为大家报告。

报告时间：12月05日 中午12：00

报告地点：南京大学鼓楼校区唐仲英楼B501

报告题目：Discrete scale invariance and log-B periodic quantum oscillations in ultra-quantum Dirac materials

摘要：The quasi-particle in Dirac materials obeys the relativistic equation, and the value of fine structure constant in Dirac materials is much larger than the value in the vacuum. Owing to the large value of fine structure constant, the Coulomb attraction gives rise to supercritical atomic collapse in analogy to the phenomena proposed to exist in super-heavy atoms. Moreover, the massless Dirac equation with Coulomb attraction also preserve the scale invariance, which in combination with the quantization effect give rise to a novel feature—the discrete scale invariance. Up to now, the discrete scale invariance confirmed in quantum systems only exist in the Efimov trimers and related physical phenomena, and generates immediate interest throughout related fields. 

In this talk, I will discuss that the two-body Weyl Hamiltonian with supercritical Coulomb attraction can give rise to Efimovian quasi-bound states with discrete scale invariance. Moreover, the magnetic field introduces a new length scale and breaks the discrete scale invariance of the system down to approximate discrete scale invariance. The formation and dissolution of Efimovian bound states largely change the densities of mobile carriers, and further result in a novel type of log-B periodic magneto-resistance oscillations in Dirac materials, which goes beyond the Landau level physics scenario.

References: arXiv:1704.00995

报告人简介：刘海文，2006年毕业于北京大学物理学院，2006年至2012年于中科院物理研究所攻读凝聚态物理学博士学位。2012年至2015年，北京大学量子材料中心博士后，助理研究员。2016年至今，北京师范大学物理学系，青年研究员。主要研究方向是低维体系中杂质、退相干效应对量子输运、量子相变性质的影响，研究系统主要集中于拓扑材料体系、二维超导薄膜、量子霍尔体系等。