How do phonons couple to a magnetic field in nonmagnetic insulators? · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
How do phonons couple to a magnetic field in nonmagnetic insulators?
Plain
Crystals such as quartz, which have no magnetic atoms, still show sideways phonon heat flow in a field, while glassy silica with the same chemistry shows none.
Precise · changed · core
Revision 1: Crystalline quartz shows a phonon thermal Hall signal, larger in cleaner crystals, while amorphous SiO2 does not (Ling, Fauque and Behnia, SciPost Physics 21, 036, 2026), and estimates based on the Lorentz force on ionic Born charges have not been shown to account for the magnitude. Derive the magnitude of $\kappa_{xy}$ in a diamagnetic crystal from a microscopic coupling (Born effective charges, molecular Berry phases, or the lattice Aharonov-Bohm phase of Behnia, SciPost Physics Core 8, 061, 2025) and explain its absence in the glass.
Revision 2: Crystalline quartz shows a phonon thermal Hall signal, larger in cleaner crystals, while amorphous $\mathrm{SiO_2}$ does not (Ling, Fauque and Behnia, SciPost Physics 21, 036, 2026), and estimates based on the Lorentz force on ionic Born charges have not been shown to account for the magnitude. Derive the magnitude of $\kappa_{xy}$ in a diamagnetic crystal from a microscopic coupling (Born effective charges, molecular Berry phases, or the lattice Aharonov-Bohm phase of Behnia, SciPost Physics Core 8, 061, 2025) and explain its absence in the glass.
Settled by
A first-principles calculation of $\kappa_{xy}$ for quartz that matches experiment in magnitude and sign and gives near-zero $\kappa_{xy}$ for silica glass.
Kind
phenomenon
Answer type
mechanism
References
(empty)
Literature status
open
Status note
A lattice Aharonov-Bohm mechanism was proposed (Behnia, SciPost Physics Core, 2025), and a phonon thermal Hall effect in nonmagnetic crystals including Si, Ge and quartz was reported in 2024 (arXiv 2404.02863); no quantitative microscopic theory exists.
Posed since
(empty)

Decisions