Abstract
A promising route to realize entangled magnetic states combines geometrical frustration with quantumtunneling 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 tripodkagome lattice material Ho3Mg2Sb3O14 unites an icelike magnetic degeneracy with quantum-tunneling terms generated by an intrinsic splitting of the Ho3 ground-state doublet, which is further coupled to a nuclear spin bath. Using neutron scattering and thermodynamic experiments, we observe a symmetrybreaking transition at T*≈ 0.32 K to a remarkable state with three peculiarities: A concurrent recovery of magnetic entropy associated with the strongly coupled electronic and nuclear degrees of freedom; a fragmentation of the spin into periodic and icelike components; and persistent inelastic magnetic excitations down to T ≈ 0.12 K. These observations deviate from expectations of classical spin fragmentation on a kagome lattice, but can be understood within a model of dipolar kagome ice under a homogeneous transverse magnetic field, which we survey with exact diagonalization on small clusters and mean-field calculations. In Ho3Mg2Sb3O14, hyperfine interactions dramatically alter the single-ion and collective properties, and suppress possible quantum correlations, rendering the fragmentation with predominantly single-ion quantum fluctuations. Our results highlight the crucial role played by hyperfine interactions in frustrated quantum magnets and motivate further investigations of the role of quantum fluctuations on partially ordered magnetic states.
| Original language | English |
|---|---|
| Article number | 031069 |
| Journal | Physical Review X |
| Volume | 10 |
| Issue number | 3 |
| DOIs | |
| State | Published - 2020 |
Funding
of Basic Energy Sciences, Scientific User Facilities Division. This work has been partially supported by the U.S. Department of Energy. ORNL is managed by UT-Battelle, LLC, under Contract No. DE-AC05-00OR22725 for the U.S. Department of Energy. The U.S. Government retains and the publisher, by accepting the article for publication, acknowledges that the U.S. Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for U.S. Government purposes. We would like to thank Cristian Batista, Owen Benton, Gia-wei Chern, Yuan Wan, Claudio Castelnovo, Laurent Chapon, Radu Coldea, Siân Dutton, Michel Gingras, James Hamp, Peter Holdsworth, Ludovic Jaubert, Gunnar Möller, Jeffrey Rau, and Han Yan for helpful discussions, and Allen Scheie for critical reading of the manuscript. We are indebted to Art Ramirez for providing heat-capacity measurements on our SS sample. The work of Z. D, X. B., J. A. M. P., E. H., and M. M. at Georgia Tech (all analysis, modeling, and interpretation work and all synthesis and measurements on SG samples) was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences Neutron Scattering Program under Award No. DE-SC0018660. The work of Z. D and H. Z. at the University of Tennessee (all synthesis and measurements on SS samples) was supported by the National Science Foundation through Grant No. DMR-2003117. H. Z acknowledges support from the NHMFL Visiting Scientist Program, which is supported by NSF Cooperative Agreement No. DMR-1157490 and the State of Florida. J. A. M. P. acknowledges support from Churchill College, Cambridge (neutron data reduction), and the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division (manuscript co-writing). The research at ISIS Neutron and Muon Source was supported by a beam-time allocation from the STFC (U.K.). The research at Oak Ridge National Laboratory’s Spallation Neutron Source and High Flux Isotope Reactor was sponsored by the U.S. DOE, Office
| Funders | Funder number |
|---|---|
| Churchill College, Cambridge | |
| ISIS | |
| State of Florida | |
| National Science Foundation | DMR-2003117, DMR-1157490 |
| U.S. Department of Energy | |
| Directorate for Mathematical and Physical Sciences | 1157490, 1350002 |
| Office of Science | DE-SC0018660 |
| Basic Energy Sciences | |
| Oak Ridge National Laboratory | DE-AC05-00OR22725 |
| University of Tennessee | |
| Division of Materials Sciences and Engineering | |
| Science and Technology Facilities Council |