Hierarchy of Exchange Interactions in the Triangular-Lattice Spin Liquid YbMgGaO4

Invited

Abstract

The spin-1/2 triangular lattice antiferromagnet YbMgGaO4 has attracted attention recently as a quantum spin-liquid candidate with the possible presence of off-diagonal anisotropic exchange interactions induced by spin-orbit coupling. Whether a quantum spin liquid is stabilized or not depends on the interplay of various exchange interactions with chemical disorder that is inherent to the layered structure of the compound. We combine time-domain terahertz spectroscopy and inelastic neutron scattering measurements in the field-polarized state of YbMgGaO4 to obtain better insight of its exchange interactions. Terahertz spectroscopy in this fashion functions as a high-field electron spin resonance and probes the spin-wave excitations at the Brillouin zone center, ideally complementing neutron scattering. A global spin-wave fit to all our spectroscopic data at fields over 4 T, informed by the analysis of the terahertz spectroscopy linewidths, yields constraints on the disorder-averaged g factors and exchange interactions. Our results paint YbMgGaO4 as an easy-plane XXZ antiferromagnet with the combined and necessary presence of subleading next-nearest neighbor and weak anisotropic off-diagonal nearest-neighbor interactions. Moreover, the obtained g factors are substantially different from previous reports. This work establishes the hierarchy of exchange interactions in YbMgGaO4 from high-field data alone and thus strongly constrains possible mechanisms responsible for the observed spin-liquid phenomenology.

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Presenters

  • Fahad Mahmood

    Johns Hopkins University, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, United States

Authors

  • Fahad Mahmood

    Johns Hopkins University, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, United States

  • Xinshu Zhang

    Johns Hopkins University

  • Marcus Daum

    School of Physics, Georgia Tech, Georgia Institute of Technology

  • Zhiling Dun

    School of Physics, Georgia Institute of Technology, Georgia Institute of Technology, School of Physics, Georgia Tech, University of Tennessee, Department of Physics, University of Tennessee

  • Joseph Paddison

    Churchill College, University of Cambridge, Cambridge, University of Cambridge, Georgia Institute of Technology, Univserity of Cambridge, Department of Physics, University of Cambridge

  • Nicholas Laurita

    Johns Hopkins University, Institute for Quantum Information and Matter, California Institute of Technology, Caltech, Department of Physics, California Institute of Technology

  • Tao Hong

    Oak Ridge National Laboratory, Neutron Scattering Division, Oak Ridge National Laboratory, Neutron Scattering Division, Oak-Ridge National Laboratory, Neutron Scattering Division, Oak Ridge National Lab

  • Haidong Zhou

    University of Tennessee, Department of Physics and Astronomy, University of Tennessee, University of Tennessee, Knoxville, Physics, University of Tennessee, Knoxville, TN, United States, Physics, University of Tennessee, Department of Physics and Astronomy, The University of Tennessee, Knoxville, Department of Physics and Astronomy, University of Tennessee, Knoxville, Department of Physics, University of Tennessee

  • Peter Armitage

    Johns Hopkins University, Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD, United States, Department of Physics and Astronomy, Johns Hopkins University

  • Martin Mourigal

    School of Physics, Georgia Institute of Technology, Georgia Institute of Technology, School of Physics, Georgia Tech