Tiancong Zhu - Purdue University

Wednesday 3 Sept 2025, 08:00 → 19:15 US/Eastern

IAMM

Wonhee Ko (University of Tennessee, Knoxville)

 

Tiancong received his PhD in physics from the Ohio State University in 2019 with Prof. Roland K. Kawakami working on spin transport and magnetism in two-dimensional materials. After that, Tiancong spent 4 years as a post-doctoral researcher at University of California, Berkeley with Prof. Michael F. Crommie working on investigating correlated and topological states with scanning tunneling microscopy. Tiancong received his BSc in Physics from Peking University, China in 2012. 

https://sites.google.com/view/zhulab/home

08:30 → 09:00 Pick up at hotel

Travel to IAMM.

09:00 → 09:30 Research Meeting

Speaker: Wonhee Ko (University of Tennessee, Knoxville)

09:30 → 10:00 Research Meeting

Speaker: Joon Sue Lee (University of Tennessee, Knoxville)

10:00 → 10:20 Talk Prep

10:20 → 11:20 Seminar: Imaging and Manipulating Quantum Anomalous Hall Edge States in Graphene Moiré Heterostructures

Moiré heterostructures have attracted significant attention in recent years for their remarkable properties in realizing novel quantum states experimentally. By carefully controlling the relative alignment between adjacent lattices, a new periodicity—the moiré lattice—emerges. This moiré lattice strongly alters the balance between electron kinetic and potential energies, giving rise to exotic quantum phases that are absent in the individual layers. In addition, owing to their inherently two-dimensional (2D) nature, the electronic and magnetic properties in these heterostructures can be directly probed by surface-sensitive microscopic and spectroscopic techniques, offering crucial experimental insights into the underlying quantum states.

In this talk, I will use engineered moire heterostructure between a sheet of monolayer and a sheet of bilayer graphene as an example to demonstrate how the quantum anomalous Hall (QAH) effect—essentially a quantum Hall effect realized without an external magnetic field—can emerge, and how new information can be acquired using scanning tunneling microscopy (STM). I will begin by discussing how STM can be employed to identify the Chern insulating states responsible for the QAH effect. I will then show how one can directly visualize one-dimensional chiral edge states in real space and track topological phase transitions between distinct Chern domains. Furthermore, I will present experimental evidence that these QAH edge states can be manipulated on demand—written, erased, and repositioned—through the combined action of the STM tip and an electrostatic back gate. Finally, I will share several new directions my group is pursuing to further advance the understanding of moiré systems using STM.

Zoom: https://tennessee.zoom.us/j/86292515289

11:30 → 12:00 Research Meeting

Speaker: Yishu Wang (University of Tennessee Knoxville)

12:00 → 14:00 Lunch

Wonhee Ko, Yishu Wang, ...

14:00 → 14:30 Research Meeting

Speaker: Hanno Weitering

14:30 → 15:00 Research Meeting

15:00 → 16:00 Research Meeting

Speaker: Ruixing Zhang (Department of Physics and Astronomy, University of Tennessee Knoxville)

16:00 → 16:30 Lab tour

16:30 → 17:00 Lab tour

17:00 → 18:30 Dinner

Wonhee Ko, Ruixing Zhang, ...