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TT: Fachverband Tiefe Temperaturen

TT 49: Frustrated Magnets: Strong Spin-Orbit Coupling I

TT 49.2: Vortrag

Mittwoch, 20. März 2024, 15:15–15:30, H 2053

Bond disorder in extended Kitaev-Heisenberg models — •Georgia Fragkopoulou and Matthias Vojta — Technische Universität Dresden

We study the effect of bond disorder in extended Kitaev-Heisenberg models on the honeycomb lattice, relevant for materials such as α-RuCl₃, in the semiclassical limit using a combination of T-matrix and real-space spin-wave approaches. Focussing on the regime of large applied magnetic field, we discuss two distinct but related disorder-induced phenomena, namely spin textures and in-gap states. Depending on whether the impurity and the field direction break the discrete lattice symmetries, impurity-induced textures either arise at arbitrary field and impurity strength and without spontaneous symmetry breaking, or they only occur beyond a certain impurity strength and are accompanied by spontaneous symmetry breaking. The latter can be understood precursors of a low-field ordered phase and induce magnetic states below the bulk gap. A finite impurity concentration turns these isolated states into impurity bands. As a result, there is a large field regime above the bulk transition to the high-field state where impurity-induced states fill the bulk spin gap. We illustrate the field dependence of these in-gap states for parameters relevant for α-RuCl₃, and we connect our results to heat-transport and NMR data which indicated their presence.

Keywords: Kitaev model; Disorder; α-RuCl3