报告题目：Quantum Griffiths Singularity in 2D Superconductors and Logarithm Law Quantum Oscillations in Ultra-quantum Semimetals

报 告 人：Jian Wang，International Center for Quantum Materials，School of Physics, Peking University

报告时间： 2:30p.m., Friday, Apr. 28th, 2017

报告地点：Lecture Hall C302, New Science Building

报告摘要：Quantum phase transition is one of most important topics in condensed matter physics. When we study the superconductor-metal transition in ultrathin crystalline Ga films grown on GaN substrate, we firstly discover quantum Griffiths singularity in two dimensional (2D) system and superconductors, which is a new quantum phase transition in 2D superconductors. This discovery is further revealed in LAO/STO (110) interface superconductors and monolaye NbSe2 films. In addition, a new class of quantum oscillations in topological semimetals beyond quantum limit has been discovered recently, where the resistivity periodically oscillates with logB. The discovery of the clear logarithm law quantum oscillations not only provides new insight into the nature of three-dimensional electronic states beyond the quantum limit but also indicates the first realization of fermionic Efimov bound states (arXiv:1704.00995).