Correlated Quantum Tunnelling of Monopoles in Spin Ice

TL;DR

This paper investigates quantum tunnelling of magnetic monopoles in spin ice materials, revealing a bimodal distribution of hopping rates and evidence for coherent many-body dynamics, advancing understanding of their low-temperature quantum behavior.

Contribution

It introduces a quantum framework for single-ion spin-flip processes in spin ice, uncovering bimodal hopping rates and potential for coherent many-body quantum dynamics.

Findings

Bimodal distribution of monopole hopping rates depending on local spin configuration

Experimental agreement with predicted hopping rate distributions

Indications of coherent many-body quantum dynamics in related materials

Abstract

The spin ice materials Ho$_{2}$Ti$_{2}$O$_{7}$ and Dy$_{2}$Ti$_{2}$O$_{7}$ are by now perhaps the best-studied classical frustrated magnets. A crucial step towards the understanding of their low temperature behaviour -- both regarding their unusual dynamical properties and the possibility of observing their quantum coherent time evolution -- is a quantitative understanding of the spin-flip processes which underpin the hopping of magnetic monopoles. We attack this problem in the framework of a quantum treatment of a single-ion subject to the crystal, exchange and dipolar fields from neighbouring ions. By studying the fundamental quantum mechanical mechanisms, we discover a bimodal distribution of hopping rates which depends on the local spin configuration, in broad agreement with rates extracted from experiment. Applying the same analysis to Pr$_{2}$Sn$_{2}$O$_{7}$ and Pr$_{2}$Zr$_{2}$O$_{7}$, we find an even more pronounced separation of timescales signalling the likelihood of coherent many-body dynamics.