Pantheon SEMPARIS Le serveur des séminaires parisiens Paris

Status Confirmed
Seminar Series RENC-THEO
Subjects cond-mat.str-el,hep-th
Date Thursday 20 June 2019
Time 10:00
Institute IHP
Seminar Room Salle 314
Speaker's Last Name Kapustin
Speaker's First Name Anton
Speaker's Email Address
Speaker's Institution Caltech
Title Thermal Hall conductance as a relative topological invariant, or detecting gravitational anomalies for lattice systems
Abstract 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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