Regensburg 2022 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 5: Frustrated Magnets – Spin Liquids

TT 5.1: Hauptvortrag

Montag, 5. September 2022, 15:00–15:30, H10

Dynamics of visons and thermal Hall effect in perturbed Kitaev models — •Aprem Joy and Achim Rosch — Institute for Theoretical Physics, University of Cologne, Cologne, Germany

A vison is an excitation of the Kitaev spin liquid which carries a Z₂ gauge flux. While immobile in the pure Kitaev model, it becomes a dynamical degree of freedom in the presence of perturbations. We study an isolated vison in the isotropic Kitaev model perturbed by a small external magnetic field h, an offdiagonal exchange interactions Γ and a Heisenberg coupling J. In the ferromagnetic Kitaev model, the dressed vison obtains a dispersion linear in Γ and h and a fully universal low-T mobility, µ=6 v_m²/T², where v_m is the velocity of Majorana fermions. In contrast, in the antiferromagnetic Kitaev model interference effects preclude coherent propagation and an incoherent Majorana-assisted hopping leads to a T-independent mobility. The motion of a single vison due to Heisenberg interactions is strongly suppressed for both signs of the Kitaev coupling. Vison bands induced by h in the AFM Kitaev model are topological and contribute to the thermal Hall effect.