Dielectric Relaxation by Quantum Critical Magnons

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 1/4 Hc and follows single-magnon energy for H > Hc, showing its magnetic origin. Our study demonstrates the electrical activity of coupled low-energy spin and lattice excitations, an example of quantum multiferroic behavior.

Automated summary

We report the observation of dielectric relaxation caused by quantum critical magnons. Complex capacitance measurements show a dissipative feature that depends on temperature due to low-energy lattice excitations, and the relaxation time follows an activation behavior. The activation energy softens near a field-tuned magnetic quantum critical point at H 1/4 Hc and follows the energy of a single magnon for H > Hc, indicating its magnetic origin. Our study demonstrates the electrical activity of coupled low-energy spin and lattice excitations, which is an example of quantum multiferroic behavior.