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Magnetic order, disorder, and excitations under pressure in the Mott Insulator Sr₂IrO₄

Li, Xiang and Cooper, S. E. and Krishnadas, A. and de la Torre, A. and Perry, R. S. and Baumberger, F. and Silevitch, D. M. and Hsieh, D. and Rosenbaum, T. F. and Feng, Yejun (2021) Magnetic order, disorder, and excitations under pressure in the Mott Insulator Sr₂IrO₄. Physical Review B, 114 (20). Art. No. L201111. ISSN 2469-9950. doi:10.1103/PhysRevB.104.L201111.

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Protected by the interplay of on-site Coulomb interactions and spin-orbit coupling, Sr₂IrO₄ at high pressure is a rare example of a Mott insulator with a paramagnetic ground state. Here, using optical Raman scattering, we measure both the phonon and magnon evolution in Sr₂IrO₄ under pressure, and identify three different magnetically-ordered phases, culminating in a spin-disordered state beyond 18 GPa. A strong first-order structural phase transition drives the magnetic evolution at ∼10 GPa with reduced structural anisotropy in the IrO₆ cages, leading to increasingly isotropic exchange interactions between the Heisenberg spins and a spin-flip transition to c-axis-aligned antiferromagnetic order. In the disordered phase of Heisenberg J_(eff) = 1/2 pseudospins, the spin excitations are quasi-elastic and continuous to 10 meV, potentially hosting a gapless quantum spin liquid in Sr₂IrO₄.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Li, Xiang0000-0002-3780-7735
de la Torre, A.0000-0002-6751-8205
Baumberger, F.0000-0001-7104-7541
Silevitch, D. M.0000-0002-6347-3513
Hsieh, D.0000-0002-0812-955X
Feng, Yejun0000-0003-3667-056X
Alternate Title:Magnetic order, disorder, and excitations under pressure in the Mott Insulator Sr2IrO4
Additional Information:© 2021 The Author(s). 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. (Received 7 October 2021; revised 31 October 2021; accepted 2 November 2021; published 19 November 2021) We thank G. Stenning and D. Nye for help with the instruments in the Materials Characterisation Laboratory at the ISIS Neutron and Muon Source. Y.F. acknowledges support from the Okinawa Institute of Science and Technology Graduate University, with subsidy funding from the Cabinet Office, Government of Japan. X.L., D.M.S., and T.F.R. acknowledge support from Air Force Office of Scientific Research Grant No. FA9550-20-1-0263. D.H. acknowledges support from Department of Energy Grant No. DE-SC0010533. F.B. was supported by the Swiss National Science Foundation. A.d.l.T. acknowledges support from the Swiss National Science Foundation through an Early Postdoc Mobility Fellowship (P2GEP2_165044).
Funding AgencyGrant Number
Okinawa Institute of Science and TechnologyUNSPECIFIED
Air Force Office of Scientific Research (AFOSR)FA9550-20-1-0263
Department of Energy (DOE)DE-SC0010533
Swiss National Science Foundation (SNSF)P2GEP2_165044
Issue or Number:20
Record Number:CaltechAUTHORS:20211130-215730151
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:112108
Deposited By: George Porter
Deposited On:01 Dec 2021 20:08
Last Modified:11 Jan 2022 22:27

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