Princeton University

Abstract:

Many topological phases of matter are characterized by gapless boundary modes that can be dramatically modified in the presence of strong electron-electron interactions. Even for the long-studied topological edge modes of quantum Hall phases, the nature of such interaction-induced changes has been elusive. A key experimental challenge has been the lack of direct information about the internal structure of edge states on the relevant length scales, which is often further confounded by disorder at the edge. In this talk, I will discuss our recent efforts in using scanning tunneling microscopy (STM) to directly image pristine electrostatically defined quantum Hall edge states in monolayer graphene. Leveraging the high spatial and energy resolution of STM, we demonstrate how correlations dictate the structures of edge channels on both magnetic and atomic length scales. For integer quantum Hall states in the zeroth Landau level, we show that interactions renormalize the edge velocity, dictate the spatial profile for copropagating edge modes, and result in unexpected valley polarization for the edge states that can differ from those of the bulk states. While some of our findings can be understood using a mean-field picture for interactions, they also demonstrate breakdown of this picture, highlighting the roles of edge fluctuations and inter-edge-channel couplings. We also extend our measurements to spatially resolve the edge state of fractional quantum Hall phases and detect signatures of interactions in tunneling spectroscopy of such chiral Luttinger liquid. Our study establishes STM spectroscopic imaging as a promising tool for exploring physics at the edge of the rapidly expanding 2D topological phases, such as the newly realized fractional Chern insulators.

Brief CV of Dr. Jiachen Yu：

Dr. Jiachen Yu earned his B.S. in Physics with distinction from Peking University in 2017. In the same year he began his graduate studies at Stanford University under the supervision of Professor Benjamin Feldman. His doctoral research focused on using scanning single-electron transistor to probe the local electronic compressibility of twisted bilayer graphene and semiconductor moiré systems. After completing his Ph.D. in 2023, he joined Professor Ali Yazdani’s group at Princeton University as a PCCM postdoctoral fellow. In this role, he develops scanning tunneling microscopy experiments to investigate engineered nanostructures in two dimensional materials.

腾讯会议ID：228-755-980

会议密码：0822

主持人：孟胜 研究员

联系人：傅琦 （82649469）