Chiral Gravitomagnetic Effect in Topological Superconductors and Superfluids

TL;DR

This paper predicts a novel thermal response in topological superconductors and superfluids, where mechanical rotations induce thermal currents via a gravitational axion field, expanding understanding of topological quantum effects.

Contribution

It introduces the concept of the chiral gravitomagnetic effect driven by a dynamical gravitational axion field in topological superconductors and superfluids, linking gravitational responses to topological phases.

Findings

Prediction of the chiral gravitomagnetic effect as a thermal current generated by mechanical rotation.

Demonstration of the anomalous thermal Hall effect in the bulk of topological superconductors.

Discussion of potential applications to Weyl superconductors' thermal responses.

Abstract

We theoretically search for dynamical cross-correlated responses of three-dimensional topological superconductors and superfluids. It has been suggested that a gravitational topological term, which is analogous to the theta term in topological insulators, can be derived in three-dimensional time-reversal invariant topological superconductors and superfluids, and that the dynamical gravitational axion field can be realized by the fluctuation of the relative phase, i.e., by the Leggett mode between topological $p$-wave pairing and conventional $s$-wave pairing. In the presence of the dynamical gravitational axion field, we propose the emergence of the "chiral gravitomagnetic effect", a thermal current generation by gravitomagnetic fields, i.e., by mechanical rotations. This effect can be regarded as a thermal counterpart of the chiral magnetic effect which has been studied mainly in Weyl semimetals. We also show the occurrence of the anomalous thermal Hall effect in the bulk. We discuss a possible application of our study to the thermal responses of Weyl superconductors.