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Dielectric Relaxation by Quantum Critical Magnons
Daniel Flavián1, Pavel A Volkov2,3,4, S Hayashida1
1Laboratory for Solid State Physics, ETH Zürich, 8093 Zürich, Switzerland.
Abstract:
We report the experimental observation of dielectric relaxation by quantum critical magnons. Complex capacitance measurements reveal a dissipative feature with a temperature-dependent amplitude due to low-energy lattice excitations and an activation behavior of the relaxation time. The activation energy softens close to a field-tuned magnetic quantum critical point at H=H_{c} and follows single-magnon energy for H>H_{c}, showing its magnetic origin. Our study demonstrates the electrical activity of coupled low-energy spin and lattice excitations, an example of quantum multiferroic behavior.
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