Thermal Hall effect from a twodimensional Schwinger boson gas with Rashba spinorbit interaction: Application to ferromagnets with inplane DzyaloshinskiiMoriya interaction
Abstract
Recently, uncovering the sources of the thermal Hall effect in insulators has become an important issue. In the case of ferromagnetic insulators, it is well known that the DzyaloshinskiiMoriya (DM) interaction can induce a magnon thermal Hall effect. Specifically, the DM vector parallel to the magnetization direction induces complex magnon hopping amplitudes, so that magnons act as if they feel Lorentz force. However, the DM vector which is orthogonal to the magnetization direction has hitherto been neglected as a possible source of magnon thermal Hall effect. This is because they play no role in the linear spin wave theory, an often invoked approximation when computing the magnon thermal Hall effect. Here, we challenge this expectation by presenting a selfconsistent Schwinger boson meanfield study of twodimensional magnets with ferromagnetic Heisenberg interaction and inplane DM interaction. We find that the relevant Schwinger boson meanfield Hamiltonian takes the form of a twodimensional electron gas with Rashba spinorbit interaction, which is known to show an anomalous Hall effect, spin Hall effect, and RashbaEdelstein effect, whose thermal counterparts also appear in our system. Importantly, the thermal Hall effect can be induced when outofplane magnetic field is applied and persists even when the magnetic field is large, so that the spins are significantly polarized, and the linear spin wave theory is expected to be a reasonable approximation. Since the linear spin wave theory predicts a vanishing thermal Hall effect, our result implies that a linear spin wave is not a sufficient approximation and that magnonmagnon interaction must be taken into account to predict the correct thermal Hall conductivity.
 Publication:

Physical Review B
 Pub Date:
 December 2020
 DOI:
 10.1103/PhysRevB.102.214421
 arXiv:
 arXiv:2009.09621
 Bibcode:
 2020PhRvB.102u4421P
 Keywords:

 Condensed Matter  Strongly Correlated Electrons;
 Condensed Matter  Mesoscale and Nanoscale Physics
 EPrint:
 5+2 pages, 4 figures