Quantum-Classical Reentrant Relaxation Crossover in Dy2Ti2O7 Spin-Ice

TL;DR

This study investigates spin relaxation in Dy2Ti2O7 spin ice, revealing a crossover from thermal to quantum relaxation below 13 K and a collective relaxation behavior below 4 K, highlighting complex quantum-classical interplay.

Contribution

It demonstrates a reentrant relaxation crossover in Dy2Ti2O7, combining thermal, quantum, and collective effects in spin relaxation mechanisms.

Findings

Relaxation time is thermally activated above 13 K.

Below 13 K, relaxation becomes temperature independent, indicating quantum tunneling.

Below 4 K, relaxation time increases sharply, showing collective spin behavior.

Abstract

We have studied spin relaxation in the spin ice compound Dy2Ti2O7 through measurements of the a.c. magnetic susceptibility. While the characteristic spin relaxation time is thermally activated at high temperatures, it becomes almost temperature independent below Tcross ~ 13 K, suggesting that quantum tunneling dominates the relaxation process below that temperature. As the low-entropy spin ice state develops below Tice ~ 4 K, the spin relaxation time increases sharply with decreasing temperature, suggesting the emergence of a collective degree of freedom for which thermal relaxation processes again become important as the spins become highly correlated.