Topological thermal Hall effect for topological excitations in spin liquid: Emergent Lorentz force on the spinons

Abstract

We study the origin of Lorentz force on the spinons in a U(1) spin liquid. We are partly inspired by the previous observation of gauge field correlation in the pairwise spin correlation using the neutron scattering measurement by P.A. Lee an N. Nagaosa [PhysRevB 87,064423(2013)] when the Dzyaloshinskii-Moriya interaction intertwines with the lattice geometry. We extend this observation to the Lorentz force that exerts on the (neutral) spinons. The external magnetic field, that polarizes the spins, effectively generates an internal U(1) gauge flux for the spinons and twists the spinon motion through the Dzyaloshinskii-Moriya interaction. Such a mechanism for the emergent Lorentz force differs fundamentally from the induction of the internal U(1) gauge flux in the weak Mott insulating regime from the charge fluctuations. We apply this understanding to the specific case of spinon metals on the kagome lattice. Our suggestion of emergent Lorentz force generation and the resulting topological thermal Hall effect may apply broadly to other non-centrosymmetric spin liquids with Dzyaloshinskii-Moriya interaction. We discuss the relevance with the thermal Hall transport in kagome materials volborthite and kapellasite.