Quantum versus classical effects at zero and finite temperature in the quantum pyrochlore Yb₂Ti₂O₇

We study the finite temperature properties of the candidate quantum spin ice material Yb₂Ti₂O₇ within the framework of an anisotropic nearest-neighbor spin 1/2 model on the pyrochlore lattice. Using finite temperature Lanczos and classical Monte Carlo methods, we highlight the importance of quantum mechanical effects for establishing the existence and location of the low-temperature ordering transition [1]. We perform simulations of the 32 site cluster, which capture the essential features of the specific heat curve seen in the cleanest known samples of this material. Focusing on recent experimental findings, we address the question of how the phase boundary between the ferromagnetic and paramagnetic phases changes when subjected to a magnetic field. Quantum mechanical effects explain discrepancies observed with a completely classical treatment and are at the heart of the observed reentrant lobed phase diagram. We also develop a qualitative understanding of the existence of a ferromagnet by relating it to its counterpart that exists in the vicinity of the classical ice manifold.

[1] HJC, arXiv:1710.02234