Phonon Hall effect in ionic crystals in the presence of static magnetic field

TL;DR

This paper investigates the phonon Hall effect in ionic crystals under static magnetic fields, providing exact calculations of thermal conductivity and revealing that the effect occurs even in nonmagnetic crystals like NaCl, with unique temperature and magnetic field dependencies.

Contribution

It presents an exact Green-Kubo based calculation of phonon Hall effect in ionic crystals considering both positive and negative phonon frequencies, including nonmagnetic materials.

Findings

PHE occurs in NaCl despite small magnitude

Off-diagonal thermal conductivity changes sign at high magnetic fields

Diverges as 1/T at low temperatures

Abstract

We study phonon Hall effect (PHE) for ionic crystals in the presence of static magnetic field. Using Green-Kubo formula, we present an exact calculation of thermal conductivity tensor by considering both positive and negative frequency phonons. Numerical results are shown for some lattices such as hexagonal lattices, triangular lattices, and square lattices. We find that the PHE occurs on the nonmagnetic ionic crystal NaCl, although the magnitude is very small which is due to the tiny charge-to-mass ratio of the ions. The off-diagonal thermal conductivity is finite for nonzero magnetic field and changes sign for high value of magnetic field at high temperature. We also found that the off-diagonal thermal conductivity diverges as $\pm{1/T}$ at low temperature.