Observation of a Nematic Quantum Hall Liquid on the Surface of Bismuth

TL;DR

This paper reports the direct observation of a nematic quantum Hall liquid on Bismuth's surface, revealing anisotropic wavefunctions and valley polarization due to symmetry breaking in high magnetic fields.

Contribution

It provides the first direct imaging of nematic quantum Hall states and their wavefunctions on a bismuth surface, demonstrating symmetry breaking and valley polarization.

Findings

Identification of three valley-polarized quantum Hall states.

Imaging of anisotropic Landau level wavefunctions.

Evidence of a nematic electronic phase.

Abstract

Nematic quantum fluids with wavefunctions that break the underlying crystalline symmetry can form in interacting electronic systems. We examine the quantum Hall states that arise in high magnetic fields from anisotropic hole pockets on the Bi(111) surface. Spectroscopy performed with a scanning tunneling microscope shows that a combination of local strain and many-body Coulomb interactions lift the six-fold Landau level (LL) degeneracy to form three valley-polarized quantum Hall states. We image the resulting anisotropic LL wavefunctions and show that they have a different orientation for each broken-symmetry state. The wavefunctions correspond precisely to those expected from pairs of hole valleys and provide a direct spatial signature of a nematic electronic phase.