Thermal Hall effects in quantum magnets

Y. Kasahara, Kaori Sugii, Takafumi Ohnishi +8 more

Adam Iaizzi

Jixun K. Ding, Emily Z. Zhang, Wen O. Wang +4 more

In light of recent experimental data indicating a substantial thermal Hall effect in square lattice antiferromagnetic Mott insulators, we investigate whether a simple Mott insulator can sustain a finite thermal Hall effect. We verify that the answer is "no" if one performs calculations within a spin-only low-energy effective spin model with noninteracting magnons. However, by performing determinant quantum Monte Carlo simulations, we show the single-band t-t^{'}-U Hubbard model coupled to an orbital magnetic field does support a finite thermal Hall effect when t^{'}≠0 and B≠0 in the Mott insulating phase. We argue that the (carrier agnostic) necessary conditions for observing a finite thermal Hall effect are time-reversal and particle-hole symmetry breaking. By considering magnon-magnon scattering using a semiclassical Boltzmann analysis, we illustrate a physical mechanism by which finite transverse thermal conductivity may arise, consistent with our symmetry argument and numerical results. Our results indicate that square and triangular lattices with SU(2) symmetry can support a finite thermal Hall effect and call for a critical reexamination of thermal Hall effect data in insulating magnets, as the magnon contribution should not be excluded a priori.

Wolfgang Ketterle

Aman Kumar, Vikram Tripathi

Historically, analytical treatments for the thermal Hall effect of many-body systems have been based around an underlying quasiparticle assumption. The authors introduce here a new purification-based tensor network method for the thermal Hall response of gapped systems, making no prior quasiparticle assumption. Motivated by reports of half-quantized thermal Hall response of Kitaev materials near field-suppressed magnetic order, the authors calculate the thermal Hall response in this parameter regime and find that it is large, but non-universal, ruling out the possibility of a revival of Ising topological order and a Majorana Hall state through this route.

C. Broholm, G. Aeppli