Dielectric relaxation by quantum critical magnons

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.

6 pages, 4 figures (SM 7 pages, 6 figures)

References in corpus (5)

• Spin current and magneto-electric effect in non-collinear magnets
• Hybrid quantum systems based on magnonics
• Bose-Einstein Condensation in Magnetic Insulators
• Electrically driven spin excitation in a ferroelectric magnet DyMnO_3
• Terahertz spectroscopy of electromagnons in Eu_{1-x}Y_xMnO_3