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Approaching the quantum critical point in a highly correlated all-in–all-out antiferromagnet

Yishu Wang, T. F. Rosenbaum, D. Prabhakaran, A. T. Boothroyd, and Yejun Feng
Phys. Rev. B 101, 220404(R) – Published 4 June 2020
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Abstract

Continuous quantum phase transition involving all-in–all-out (AIAO) antiferromagnetic order in strongly spin-orbit-coupled 5d compounds could give rise to various exotic electronic phases and strongly-coupled quantum critical phenomena. Here we experimentally trace the AIAO spin order in Sm2Ir2O7 using direct resonant x-ray magnetic diffraction techniques under high pressure. The magnetic order is suppressed at a critical pressure Pc=6.30GPa, while the lattice symmetry remains in the cubic Fd3m space group across the quantum critical point. Comparing pressure tuning and the chemical series R2Ir2O7 reveals that the approach to the AIAO quantum phase transition is characterized by contrasting evolutions of the pyrochlore lattice constant a and the trigonal distortion surrounding individual Ir moments, which affects the 5d bandwidth and the Ising anisotropy, respectively. We posit that the opposite effects of pressure and chemical tuning lead to spin fluctuations with different Ising and Heisenberg character in the quantum critical region. Finally, the observed low pressure scale of the AIAO quantum phase transition in Sm2Ir2O7 identifies a circumscribed region of P-T space for investigating the putative magnetic Weyl semimetal state.

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  • Received 11 October 2019
  • Revised 13 May 2020
  • Accepted 15 May 2020

DOI:https://doi.org/10.1103/PhysRevB.101.220404

©2020 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Yishu Wang1,2, T. F. Rosenbaum1, D. Prabhakaran3, A. T. Boothroyd3, and Yejun Feng1,4,*

  • 1Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, California 91125, USA
  • 2The Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA
  • 3Department of Physics, University of Oxford, Clarendon Laboratory, Oxford OX1 3PU, United Kingdom
  • 4Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa 904-0495, Japan

  • *yejun@oist.jp

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Issue

Vol. 101, Iss. 22 — 1 June 2020

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