Intrinsic and extrinsic nonstationary field-driven processes in the spin-ice compound Dy2Ti2O7

TL;DR

This study investigates how ultrasound waves reveal nonstationary magnetic field-driven processes in Dy2Ti2O7 spin ice, showing anomalies and hysteresis linked to emergent quasiparticles at very low temperatures.

Contribution

It provides new insights into the non-equilibrium dynamics and field-driven processes in spin ice, highlighting intrinsic and extrinsic regimes through ultrasound measurements.

Findings

Observation of anomalies in sound velocity and attenuation below 500 mK.

Identification of intrinsic and extrinsic regimes via field sweep rate dependence.

Detection of hysteresis and peaks associated with emergent quasiparticles.

Abstract

Nonequilibrium processes are probed by ultrasound waves in the spin-ice material Dy2Ti2O7 at low temperatures. The sound velocity and the sound attenuation exhibit a number of anomalies versus applied magnetic field for temperatures below the "freezing" temperature of ~500 mK. These robust anomalies can be seen for longitudinal and transverse acoustic modes for different field directions. The anomalies show a broad hysteresis. Most notable are peaks in the sound velocity, which exhibit two distinct regimes: an intrinsic (extrinsic) one in which the data collapse for different sweep rates when plotted as function of field strength (time). We discuss our observations in context of the emergent quasiparticles which govern the low-temperature dynamics of the spin ice.