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Intensive study of RuCl3 has been motivated recently by signatures of strongly anisotropic and frustrated interactions reminiscent of the Kitaev honeycomb model. Even though RuCl3 orders antiferromagnetically at zero field, it exhibits a broad continuum of magnetic excitations, which coexists with sharp magnons in different regions of k-space. Many works have interpreted the breakdown of magnons at certain wavevectors as a signature of proximity to the Kitaev spin liquid. A similar interpretation has been suggested for the continuum of excitations arising when magnetic order is suppressed either by high temperature, or in-plane magnetic fields. In order to evaluate these proposals, it is important to understand the underlying interactions and energy scales in RuCl3 in the context of recent experiments. We have considered the dynamical response and stability of magnons at zero and finite field with respect to the full range of realistic magnetic interactions suggested by recent ab-initio calculations. Combining extensive exact diagonalization studies with semiclassical analysis, we will address the (i) relevant mechanisms for magnon breakdown, (ii) origin and robustness of the continuum, (iii) evolution of the spectra under applied field, and (iv) possible nature of the field-induced state.

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Stephen Winter, Goethe Universität Frankfurt
Seminar Room of the Institute of Physics II
Contact: Ciaran Hickey