Of chain-based order and quantum spin liquids in dipolar spin ice

TL;DR

This paper investigates how dipolar interactions, exchange interactions, and quantum fluctuations influence the ground state of dipolar spin ice, revealing that quantum effects can stabilize a spin-liquid state even at low temperatures.

Contribution

It introduces a new organizational principle where ordered states are selected from chain states with screened dipolar interactions, and demonstrates that small quantum tunneling stabilizes a quantum spin-liquid ground state.

Findings

Ordered ground states are selected from chain states with screened dipolar interactions.

Small quantum tunneling g stabilizes a quantum spin-liquid ground state.

Phase diagrams show the transition between classical and quantum regimes.

Abstract

Recent experiments on the spin-ice material Dy2Ti2O7 suggest that the Pauling "ice entropy", characteristic of its classical Coulombic spin-liquid state, may be lost at low temperatures [D. Pomaranski et al., Nature Phys. 9, 353 (2013)]. However, despite nearly two decades of intensive study, the nature of the equilibrium ground state of spin ice remains uncertain. Here we explore how long-range dipolar interactions D, short-range exchange interactions, and quantum fluctuations combine to determine the ground state of dipolar spin ice. We identify a new organisational principle, namely that ordered ground states are selected from a set of "chain states" in which dipolar interactions are exponentially screened. Using both quantum and classical Monte Carlo simulation, we establish phase diagrams as a function of quantum tunneling g, and temperature T, and find that only a very small g_c << D is needed to stabilize a quantum spin-liquid ground state. We discuss the implications of these results for Dy2Ti2O7.