86th Annual Meeting of the APS Southeastern Section
Volume 64, Number 19
Thursday–Saturday, November 7–9, 2019;
Wrightsville Beach, North Carolina
Session H02: Frustrated Quantum Magnets
8:00 AM–10:00 AM,
Saturday, November 9, 2019
Holiday Inn Resort
Room: Airlie/Tidewater
Chair: Lin Hao, University of Tennessee
Abstract: H02.00002 : Quantum versus Classical Spin Fragmentation In Dipolar Kagome Ice Ho3Mg2Sb3O14*
8:30 AM–9:00 AM
Preview Abstract
Abstract
Author:
Zhiling Dun
(Georgia Institute of Technology)
A promising route to realize entangled magnetic states combines geometrical frustration with quantum-tunneling effects. Spin-ice materials are canonical examples of frustration, and Ising spins in a transverse magnetic field are the simplest many-body model of quantum tunneling. Here, we show that the tripod kagome lattice material Ho${_3}$Mg${_2}$Sb${_3}$O${_{14}}$ unites an ice-like magnetic degeneracy with quantum-tunneling terms generated by an intrinsic splitting of the Ho$^{3+}$ ground-state doublet, which is further coupled to a nuclear spin bath.
Using neutron scattering and thermodynamic experiments, we observe a symmetry-breaking transition at $T^{\ast}\approx0.32$ K to a remarkable quantum state with three peculiarities: a dramatic recovery of magnetic entropy associated with the strongly coupled electronic and nuclear degrees of freedom; a fragmentation of the spin into periodic and ice-like components strongly affected by quantum fluctuations; and persistent inelastic magnetic excitation spectrum down to $T\approx0.12$ K. These observations deviate from expectations of classical spin fragmentation physics on a kagome lattice, which can be alternatively understood in a framework of dipolar kagome ice under a homogeneous transverse field.
Using various theoretical approaches, including random phase approximation, mean-field approximation, and exact diagonalization, our calculations establish the existence of a highly entangled fragmented state in a region where the transverse field remains a perturbation to the dipole-dipole interactions, which we coin as a quantum spin fragmented state. However, hyperfine interactions play a crucial role in suppressing quantum correlations and dramatically alter the single-ion and collective properties of Ho${_3}$Mg${_2}$Sb${_3}$O${_{14}}$. Our results thus highlight the crucial role played by hyperfine interactions in frustrated quantum magnets and motivate further theoretical investigations of the interplay between spin fragmentation and coherent quantum tunneling.
[Reference: Z.L. Dun, X. Bai, J.A.M. Paddison, et al., arXiv:1806.04081]
*The work at Georgia Tech and U. Tennessee was supported by the Department of Energy (DE-SC0018660) and National Science Foundation (DMR-1350002), respectively.