Quantum Hall Physics in a Three-Dimensional Magnetic Crystal

by Dr Zexun Lin（林泽勋） (University of Cambridge)

Wednesday 30 Sept 2026, 10:00 → 11:00 Asia/Shanghai

Tsung-Dao Lee Institute/N4F-N400 - meeting room (Tsung-Dao Lee Institute)

Host: Prof. Baiqing Lyu  

Venue: TDLI Meeting Room N400

 

Abstract:

The quantum Hall effect is usually associated with two-dimensional electron systems. In three dimensions, a magnetic field alone generally produces dispersive Landau bands rather than a bulk-gapped Hall insulator, while familiar constructions often begin with stacked quantum Hall layers. I will present a different route in a periodic pyrochlore crystal, where a [111] magnetic field selects a three-in/one-out texture of localized moments. Through Kondo exchange, this texture effectively produces a noncoplanar four-sublattice exchange field for itinerant electrons, generating complex hopping amplitudes that mix the compact localized states into weakly dispersive bands. Remarkably, the magnetic texture alone can stabilize a globally gapped phase throughout the three-dimensional Brillouin zone.  The resulting phase is a three-dimensional quantum Hall insulator with a quantized Hall response characterized by a reciprocal-space Hall vector. I will discuss its microscopic origin, bulk transport signatures, and the properties of its chiral metallic surface states.

 

Biography:

Zexun Lin is a postdoctoral researcher in the TCM Group at the Cavendish Laboratory, University of Cambridge, where he works with Prof. Nigel Cooper and Claudio Castelnovo. He received his PhD in physics from the University of Texas at Austin, where he was supervised by Prof. Greg Fiete and Allan MacDonald. His current research interests include three-dimensional quantum Hall physics in pyrochlore systems, Wigner crystallization and fractionalization in moire transition-metal dichalcogenides, and cavity quantum materials.