Flavor Nernst effects in quantum paramagnets

TL;DR

This paper explores the flavor Nernst effect in quantum paramagnets, revealing how crystal electric field excitations and spin-orbit coupling can generate Hall-type thermal spin transport, with implications for topological spin phenomena.

Contribution

It introduces the concept of flavor Nernst effect in quantum paramagnets and demonstrates it in a 2D pyrochlore thin film using linear flavor-wave theory.

Findings

Demonstrated the FNE in a 2D pyrochlore thin film

Showed the FNE depends on temperature, anisotropy, and external fields

Linked FNE to the Berry curvature of CEF excitations

Abstract

Recent advances in spin transport research have highlighted the potential of quantum paramagnets as platforms for exploring novel phenomena and developing next-generation technologies. In this paper, we investigate the flavor Nernst effect (FNE) in quantum paramagnets, focusing on the Hall-type thermal spin transport of crystal electric field (CEF) excitations with spin-orbit couplings. As a proof of principle, we investigate the quantum paramagnetic ground state in an effective spin-1 Hamiltonian with Dzyaloshinskii-Moriya interactions and a large hard-axis anisotropy. We employ linear flavor-wave theory to analyze the low-energy excitations, and obtain the flavor Nernst coefficients from the linear response theory. We demonstrate the FNE in a 2D pyrochlore thin film with an all-in-all-out Ising axis configuration, and investigate their dependence on temperature, anisotropy, DM interaction, and external fields. Our results reveal the connection between the FNE and the Berry curvature of the CEF excitations, suggesting potential applications in manipulating thermal spin currents and exploring topological spin transport phenomena in quantum paramagnets.