Abstract:
A quantum phase transition (QPT) is described by a non-analyticity of the system's ground state energy. While a topological phase transition (TPT) is characterized by a bulk topological invariant in the bulk with associated edge modes in the boundary. It was known that a QPT is not necessarily a TPT, but it was also widely believed that a TPT must be also a QPT. Here we find a first example of a TPT which is not a QPT. It is a TPT from an odd Chern metal (OCM) to a band metal. There is a universal, but un-quantized Hall conductance jumps across such a TPT with no singularity to any orders in the ground state energy. We demonstrate these findings in a quantum anomalous Hall (QAH) system subject to a non-centrosymmetric term. Inside the OCM, as tuning the angle of the direction of the non-centrosymmetric term with respect to the edge in a long strip geometry, there is an edge transition from two edge modes flowing along the same longitudinal direction to no edge modes. Concomitantly, the OCM supports counter-flowing bulk currents and anisotropic optical conductivities. The effects of interactions and disorders are briefly discussed. The experimental detections under 2-or 4-terminal leads are presented.

About the speaker:
Prof. Ye received his Ph.D from Yale University. After spending many years in doing research, teaching and services in R-1 research universities in US and China, He joined the faculty as a chair professor at the newly found Great Bay University in Dongguan, Guangdong, China in July 2023. He is a condensed matter theorist working on the interdisciplinary field of condensed matter, quantum optics, cold atoms and non-relativistic quantum field theory and conformal field theory. Recently, he has been particularly interested to explore possible deep connections among quantum/topological phases, Sachdev-Ye-Kitaev models and quantum black holes from material's point of views.

Inviter: 许杨研究员

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