Generic Field-Driven Phenomena in Kitaev Spin Liquids: Canted Magnetism and Proximate Spin Liquid Physics

Abstract

Topological spin liquids in two spatial dimensions are stable phases in the presence of a small magnetic field, but may give way to field-induced phenomena at intermediate field strengths. Sandwiched between the lowfield spin liquid physics and the high-field spin-polarized phase, the exploration of magnetic phenomena in this intermediate regime however often remains elusive to controlled analytical approaches. Here we numerically study such intermediate-field magnetic phenomena for two representative Kitaev models (on the square-octagon and decorated honeycomb lattice) that exhibit either Abelian or non-Abelian topological order in the low-field limit. Using a combination of exact diagonalization and density matrix renormalization group techniques, as well as linear spin-wave theory, we establish the generic features of Kitaev spin liquids in an external magnetic field. While ferromagnetic models typically exhibit a direct transition to the polarized state at a relatively low field strength, antiferromagnetic couplings not only substantially stabilizes the topological spin liquid phase, but generically lead to the emergence of a distinct field-induced intermediate regime, separated by a crossover from the high-field polarized regime. Our results suggest that, for most lattice geometries, this regime generically exhibits significant spin canting, antiferromagnetic spin-spin correlations, and an extended proximate spin liquid regime at finite temperatures. Notably, we identify a symmetry obstruction in the original honeycomb Kitaev model that prevents, at least for certain field directions, the formation of such canted magnetism without breaking symmetries -consistent with the recent numerical observation of an extended gapless spin liquid in this case.

Symmetry Analysis of Tensors in the Honeycomb Lattice of Edge-Sharing Octahedra

“…Recently, a half-quantized thermal Hall effect (THE) was observed in the field-induced QSL phase of α-RuCl 3 [33,34] for the magnetic field applied along different directions. Several theoretical works have also explored the effect of a magnetic field along different directions on the Kitaev QSL [35][36][37][38][39][40][41][42][43][44]. Motivated by these experiments, we perform a symmetry-based tensor analysis on the honeycomb lattice of edge-sharing octahedra (Fig.…”