摘要

 It is well known that there are two classes of quantum oscillations. One is magnetic field B periodic oscillations, such as Aharonov-Bohm effect for mesoscopic system and Little Parks oscillations for superconducting systems. The other one is 1/B periodic Shubnikov-deHaas and deHaas van-Alphen oscillations from quantized Landau levels. We discover a new class of quantum oscillations beyond quantum limit in topological materials by magnetoresistance measurements up to ultrahigh magnetic field, which show exotic log B periodic oscillations, i.e. discrete scale invariance [1]. The observed log B quantum oscillations can be explained by relativistic quantum quasi-bound states of supercritical atomic collapse [1] and have been further detected in Hall traces of different topological materials [2].

Quantum metal state, quantum Griffiths singularity and Ising superconductivity have become three most important topics in crystalline 2D superconductors [3]. I would like to talk about our recent achievements in these directions [4-8].

报告人简介

Jian Wang, Changjiang Distinguished Professor of China's Ministry of Education, received his bachelor’s degree in Physics from Shandong University in 2001, and PhD degree in condensed matter physics from Institute of Physics, Chinese Academy of Sciences in 2007. From 2006 to 2011, he worked as a Postdoc and Research Associate at Penn State University, USA. He became a Professor at Peking University in 2017. He was selected to Changjiang Distinguished Professor of China's Ministry of Education in 2016 and Chief Scientist for National Key R&D Program of China in 2018. He won Sir Martin Wood China Prize in 2015. His current research interests are qauntum transport properties of low dimensional superconductors and topological materials. Jian Wang with collaborators discovered log-periodic quantum oscillations in a solid state system, quantum Griffiths singularity in 2D superconductors, tip-induced unconventional superconductivity in topological materials, interface-modulated Ising superconductivity, as well as for the first time demonstrated high Tc in one unit cell thick FeSe films by direct transport and Meissner evidences, revealed eletron-electron interaction in topological materials, and studied the heterostructures of topological/ferromagnetic materials and superconductors etc as one of the pioneers. In recent years, he has authored more than 70 papers including Science, Science Advances, Nature Materials, Nature Physics, Nature Nanotechnology, Nature Communications, PNAS, Physical Review X, Physical Review Letters, Nano Letters, JACS, Advanced Materials etc. Jian Wang’s lab at Peking University possesses low temperature scanning tunneling microcopy/spectroscopy-molecular beam epitaxy combined ultrahigh vacuum system, ultralow temperature-high magnetic field measurement system etc.