The phonon thermal Hall angle in black phosphorus.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 36823192.
- Also identified by DOI 10.1038/s41467-023-36750-3 and PMC identifier 9950068.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The origin of phonon thermal Hall Effect (THE) observed in a variety of insulators is yet to be identified. Here, we report on the observation of a thermal Hall conductivity in a non-magnetic elemental insulator, with an amplitude exceeding what has been previously observed. In black phosphorus (BP), the longitudinal (κ<sub>ii</sub>), and the transverse, κ<sub>ij</sub>, thermal conductivities peak at the same temperature and at this peak temperature, the κ<sub>ij</sub>/κ<sub>jj</sub>/B is ≈ 10<sup>-4</sup>-10<sup>-3</sup> T<sup>-1</sup>. Both these features are shared by other insulators displaying THE, despite an absolute amplitude spreading over three orders of magnitude. The absence of correlation between the thermal Hall angle and the phonon mean-free-path imposes a severe constraint for theoretical scenarios of THE. We show that in BP a longitudinal and a transverse acoustic phonon mode anti-cross, facilitating wave-like transport across modes. The anisotropic charge distribution surrounding atomic bonds can pave the way for coupling between phonons and the magnetic field.