Pantheon SEMPARIS Le serveur des séminaires parisiens Paris

Statut Confirmé
Domaines cond-mat.str-el,hep-th
Date Jeudi 20 Juin 2019
Heure 10:00
Institut IHP
Salle Salle 314
Nom de l'orateur Kapustin
Prenom de l'orateur Anton
Addresse email de l'orateur
Institution de l'orateur Caltech
Titre Thermal Hall conductance as a relative topological invariant, or detecting gravitational anomalies for lattice systems
Résumé It is well-known that zero-temperature Hall conductance of a 2d system can be interpreted both as a bulk transport coefficient and a U(1) anomaly for the edge modes. The former interpretation allows one to write down a simple formula for it (Kubo formula). The latter interpretation explains why Hall conductance is a topological invariant. In this talk I will explain the difficulties in extending these considerations to thermal Hall conductance and how they are overcome. I argue that thermal Hall conductance should be regarded as an exact 1-form on the parameter space rather than a function. Another observation is that anomalies of edge modes can be interpreted in physical terms as violations of F. Bloch’s theorem about the absence of currents in an equilibrium state. Combining these observations, I show that low-temperature thermal Hall conductance of a gapped 2d system is robust under arbitrary deformations which do not close the gap.
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