Observation of a nematic quantum Hall liquid on the surface of bismuth

Nematic quantum fluids with wavefunctions that break the underlying crystalline symmetry can spontaneously form as a result of electronic correlations. 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 exchange interactions lift the six-fold Landau level degeneracy to form three valley-polarized quantum Hall states. We image the resulting anisotropic wavefunctions and show that they have a different orientation for each broken-symmetry state. Our measurements provide a direct spatial signature of a local domains of a nematic quantum Hall liquid. Moreover, this is the first material system where the role of electronic interactions in the formation of nematic order can be quantified and directly correlated with a microscopic theory.