Thermal Hall response: violation of gravitational analogues and Einstein relations

Abstract

The response of solids to temperature gradients is often described in terms of a gravitational analogue: the effect of a space-dependent temperature is modeled using a space dependent metric. We investigate the validity of this approach in describing the bulk response of quantum Hall states and other gapped chiral topological states. To this end, we consider the prototypical Haldane model in two different cases of (i) a space-dependent electrostatic potential and gravitational potential and (ii) a space-dependent temperature and chemical potential imprinted by a weak coupling to non-interacting electron baths and phonons. We find that the thermal analogue is \textit{invalid}; while a space dependent gravitational potential induces transverse energy currents proportional to the third derivative of the gravitational potential, the response to an analogous temperature profile vanishes in limit of weak coupling to the thermal bath. Similarly, the Einstein relation, the analogy between the electrostatic potential and the internal chemical potential, is not valid in such a setup.

In the latest version, we have added the part to include phonon baths for internal equilibration and a more realistic way to imprint a temperature profile onto the system. 17 pages (5 pages for the main text and 12 pages for the supplementary material), 8 figures (4+4)

References in corpus (5)

• Robustness of the thermal Hall effect close to half-quantization in a field-induced spin liquid state
• Thermal Hall Effect and Geometry with Torsion
• Low-energy effective theory in the bulk for transport in a topological phase
• Bulk thermal transport coefficients in a quantum Hall system and the fundamental difference between thermal and charge response
• Torsion, energy magnetization and thermal Hall effect

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