Séminaire IQ: Annulé: Mallika Randeria

Mallika Randeria

MIT

Invitée par André-Marie Tremblay

Title:Imaging nematic quantum Hall states and their interacting boundary modes

Two-dimensionalquantum Hall systems offer a versatile platform to explore the interplaybetween topology and symmetry breaking facilitated by Coulomb interactions. Inthis talk, I discuss the novel phenomena that arise from spontaneous valleyordering of bismuth surface states in a large magneticfield.  Specifically, we observe the emergence of a nematic phase whichbreaks the rotational symmetry of the underlying crystal and a ferroelectricphase that carries an in-plane electric dipole moment. We use a scanningtunneling microscope to identify and directly image the wavefunctions of thesebroken-symmetry quantum Hall phases.  Furthermore, we explore theboundary between distinct nematic domains, which host counter-propagating 1Dmodes. By changing the valley flavor and number of modes, we realize strikinglydifferent regimes where the boundary is either metallic or insulating,constrained by Coulomb interactions between these 1D modes.