imaging and Harnessing the Topological Boundary Modes

by Prof. Zhenyu Wang（王震宇） (University of Science and Technology of China)

Wednesday 15 Apr 2026, 15:00 → 16:00 Asia/Shanghai

Tsung-Dao Lee Institute/N6F-N600 - Lecture Room (Tsung-Dao Lee Institute)

Host: Prof. Baiqing Lv  

Venue: TDLI Meeting Room N600

Tencent Meeting link: https://meeting.tencent.com/dm/U4rca1Akx74A 

Meeting ID: 315522337, no password

 

Abstract:

Topologically protected edge channels show prospects for quantum devices [1]. In this talk we provide evidence for robust topological helical edge states within a novel topology named three-dimensional (3D) QSHIs. Its topology originates solely from a nonzero spin Chern number for each plane of the crystal and is realized in both bulk α-Bi4I4 with trivial symmetry indicators and α-Bi4Br4 with inversion Z4 index. We experimentally observe the edge modes at each type of monolayer and bilayer step of these materials by scanning tunneling microscopy (STM). These edges states are linearly dispersing protected by a large bulk gap spanning EF, robust against disorders and vertical stacking [2]. Based on these findings, we fabricate a novel “topological” STM tip with these materials, and show how the tunneling of the helical edge state becomes a metrological resource for atomic-scale spin sensing owing to the time-reversal-symmetry paired spin-momentum locking. As a stringent benchmark, we apply this helical tunneling spin probe to the layered altermagnetic material KV2Se2O and directly image the defining alternating spin texture in both real and momentum space [3]. 

 

References:

[1] S. Phark et al., Nano Futures 9, 032001(2025);

[2] S. Yu et al., Phys. Rev. X 14, 041048 (2024); 

[3] Z. Wang et al., arXiv: 2512.23290 (2025)

 

Biography:

Professor Zhenyu Wang obtained his PhD from Institute of Physics, Chinese Academy of Sciences, in 2015. Then he held a postdoctoral appointment at the University of Illinois Urbana-Champaign, before joining the physics faculty at University of Science and Technology of China in 2019. He became a full professor of Physics in 2023. His research interests lie in the realm of quantum materials, including unconventional superconductors, Mott insulators and topological matters. He uses the tool of STM to unravel the mysteries of these complex systems, and the fundamental goal is to directly visualize their emergent behaviors and manipulate their properties. He has Now Prof. Wang’s lab focuses on STM studies of topological superconductors and moiré superlattice where both electronic interactions and quantum geometry play the vital role in shaping their electronic properties.