Is the Yb2Ti2O7 pyrochlore a quantum spin ice?

TL;DR

This study uses numerical linked cluster expansions to analyze the specific heat and entropy of Yb2Ti2O7, revealing features consistent with quantum spin ice behavior and suggesting common physics in similar materials.

Contribution

The paper applies NLC expansions to a quantum spin ice model of Yb2Ti2O7, connecting experimental data with theoretical predictions and identifying characteristic thermodynamic features.

Findings

Good agreement between model and experimental calorimetric data.

Identification of two peaks in specific heat related to spin ice crossover and phase transition.

Weakly confined spinon-antispinon excitations in the quantum regime.

Abstract

We use numerical linked cluster (NLC) expansions to compute the specific heat, C(T), and entropy, S(T), of a quantum spin ice model of Yb2Ti2O7 using anisotropic exchange interactions recently determined from inelastic neutron scattering measurements and find good agreement with experimental calorimetric data. In the perturbative weak quantum regime, this model has a ferrimagnetic ordered ground state, with two peaks in C(T): a Schottky anomaly signalling the paramagnetic to spin ice crossover followed at lower temperature by a sharp peak accompanying a first order phase transition to the ferrimagnetic state. We suggest that the two C(T) features observed in Yb2Ti2O7 are associated with the same physics. Spin excitations in this regime consist of weakly confined spinon-antispinon pairs. We suggest that conventional ground state with exotic quantum dynamics will prove a prevalent characteristic of many real quantum spin ice materials.