안녕하세요 물리학과 사무실입니다.

Speaker: Dr. Thomas Werkmeister (Columbia University; Incoming Assistant Professor at TU Delft)

A two-dimensional (2D) electron gas subjected to large magnetic fields and low temperatures exhibits the quantum Hall effect, where current flows ballistically along the one-dimensional (1D) boundary of the system. These chiral, 1D edge currents can be exploited to construct coherent electronic interferometers, analogous to an optical Fabry-Pérot cavity, that reveal the current-carrying quasiparticles’ quantum phase. In fractional quantum Hall states, strong interactions between the 2D electrons stabilize 'anyon' quasiparticles, with fractional charges and non-trivial braiding phases, unlike conventional fermions or bosons. In this talk, I will highlight experiments to directly observe exotic anyon quasiparticles in fractional quantum Hall states through interferometry. While these experiments have been pursued in traditional semiconductor quantum wells for decades, new intrinsically 2D materials offer distinct advantages. I will present the first edge state interferometer experiments in single-atom thick graphene demonstrating the Aharonov-Bohm phase of electrons in integer quantum Hall states [1]; resolving strong correlations between edge states [2]; and directly measuring the fractional charge and Abelian anyon braiding phase in fractional quantum Hall states [3]. These experiments demonstrate how quantum coherent devices reveal phenomena that are otherwise inaccessible via electronic transport measurements and open the door for developing fault-tolerant qubits leveraging braided anyons. Future experiments will aim to discover and utilize the properties of more exotic non-Abelian anyons using improved interferometry techniques and 2D materials beyond graphene.

References: 

[1] Y. Ronen, T. Werkmeister et al. Nature Nanotechnology 16, 563–569 (2021).

[2] T. Werkmeister et al. Nature Communications 15,6533 (2024). 

[3] T. Werkmeister et al. Science 388, 730–735 (2025).

Short Bio
https://sites.google.com/view/thomas-werkmeister
Dr. Tom Werkmeister is a Simons Junior Fellow in Applied Physics at Columbia University, working on the physics of low-dimensional materials. Within condensed matter physics, he focuses on quantum states of electrons, especially those exhibiting topological order, magnetism, or superconductivity. Werkmeister studies these states by creating and measuring quantum coherent devices made from novel materials like graphene. Some of his recent devices have been fractional quantum Hall edge state interferometers and Josephson junction interferometers. More generally, he is interested in discovering better superconductors and stabilizing topological phases at higher temperatures using new materials. These material improvements are critical for emerging technologies, from topologically protected qubits for quantum computation to powerful magnets for magnetic levitation, magnetic resonance imaging, and nuclear fusion. Werkmeister received his Ph.D. in Applied Physics from Harvard University in 2025, advised by Prof. Philip Kim.