Theories for The 3D Quantum Hall Effects
The discovery of the quantum Hall effect has led to three Nobel prizes and the booming field of topological phases of quantum matter. The quantum Hall effect is usually observed in 2D. It has been a long-standing challenge to realize a quantum Hall effect in 3D.
The speaker and his research group predict a new mechanism of 3D quantum Hall effect in topological semimetals. Topological semimetals, which host topologically-protected surface states, are known as the Fermi arcs. The Fermi arcs at two opposite surfaces can form a 2D electron gas that supports a 3D quantum Hall effect. Possible signatures are observed in the topological Dirac semimetal Cd3As2 [e.g., XIU Faxian et al., Nature 565, 331 (2019)]. This 3D quantum Hall gives an example of (d-2)-dimensional boundary states in higher-order topological phases of matter.
On the other hand, the charge-density-wave mechanism of the 3D quantum Hall effect has been observed recently in ZrTe5 [ZHANG Liyuan et al., Nature 569, 537 (2019)]. The speaker and his research group develop a theory for the Charge density waves (CDW) mechanism of the 3D quantum Hall effect and coexisting meta-insulator transition. The theory can capture the main features in the experiment. More importantly, it poses a rare case, in which one magnetic field can induce an order-parameter phase transition in one dimension but a topological phase transition in other two dimensions.
About the speaker
Prof. LU Hai-Zhou obtained his PhD in Physics from the Institute for Advanced Study, Tsinghua University in 2007. He then joined the University of Hong Kong as a Postdoctoral Fellow and moved to the Southern University of Science and Technology (SUSTech) in 2015. He is currently the Chair Professor of Physics in SUSTech.
Prof. Lu's research focuses on theoretical condensed matter physics, in particular, electronic and quantum transport properties of mesoscopic systems, topological states of matter, and spintronics. His recent interest is applying quantum field theoretical methods to study the electronic transport and quantum phases in new materials. For example, topological insulator/semimetal/superconductor, 2D layered materials, weak (anti-)localization, the quantum anomalous/spin Hall effect, etc. He has more than 100 publications with a google scholar citation over 7000.
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