Abstract
The pseudospin- degrees of freedom in the pyrochlore magnet are known to possess dipole-octupole character, making it a candidate for novel quantum spin liquid ground states at low temperatures. We report new polarized neutron diffraction at low temperatures, as well as heat capacity () measurements on single crystal . The former bears both similarities and differences with that measured from the canonical dipolar spin ice compound , while the latter rises sharply at low temperatures, initially plateauing near 0.08 K, before falling off toward a high temperature zero beyond 3 K. , the dataset can be fit to the results of a quantum numerical linked cluster calculation, carried out to fourth order, that allows estimates for the terms in the near-neighbor XYZ Hamiltonian expected for such dipole-octupole pyrochlore systems. Fits of the same theory to the temperature dependence of the magnetic susceptibility and unpolarized neutron scattering complement this analysis. A comparison between the resulting best-fit numerical linked cluster calculation and the polarized neutron diffraction shows both agreement and discrepancies, mostly in the form of zone-boundary diffuse scattering in the non-spin-flip channel, which are attributed to interactions beyond near neighbors. The lack of an observed thermodynamic anomaly and the constraints on the near-neighbor XYZ Hamiltonian suggest that realizes a quantum spin liquid state at low temperatures, and one that likely resides near the boundary between dipolar and octupolar character.
- Received 4 August 2021
- Revised 8 December 2021
- Accepted 18 February 2022
DOI:https://doi.org/10.1103/PhysRevX.12.021015
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
In a quantum spin liquid, individual atomic magnetic moments, or spins, remain disordered even at absolute zero temperature while fluctuating in a quantum entangled manner. This phase of matter is of great interest, as it possesses novel excited states with which we have little familiarity. Here, we lay out the detailed case for a novel quantum spin liquid phase at low temperature in , a quantum spin liquid candidate that has gained much attention recently.
Our evidence for this rare quantum spin liquid phase comes from experimental estimates for “interaction parameters,” which provide information on how the spins interact with one another. We determine experimental values for these parameters by fitting specific heat, magnetic susceptibility, and neutron-scattering data, and we use the resulting parameters to predict the magnetic ground state for in accordance with recent theory.
The measured interaction parameters indicate a quantum spin liquid ground state near the boundary of “dipolar” and “octupolar” behavior. This suggests that possesses a quantum spin liquid phase that involves fluctuating quantum-entangled magnetic dipoles and octupoles. This is important because typical quantum spin liquids involve only dipoles.
