Abstract
Continuous quantum phase transition involving all-in–all-out (AIAO) antiferromagnetic order in strongly spin-orbit-coupled compounds could give rise to various exotic electronic phases and strongly-coupled quantum critical phenomena. Here we experimentally trace the AIAO spin order in using direct resonant x-ray magnetic diffraction techniques under high pressure. The magnetic order is suppressed at a critical pressure , while the lattice symmetry remains in the cubic space group across the quantum critical point. Comparing pressure tuning and the chemical series reveals that the approach to the AIAO quantum phase transition is characterized by contrasting evolutions of the pyrochlore lattice constant and the trigonal distortion surrounding individual Ir moments, which affects the 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 identifies a circumscribed region of P-T space for investigating the putative magnetic Weyl semimetal state.
- Received 11 October 2019
- Revised 13 May 2020
- Accepted 15 May 2020
DOI:https://doi.org/10.1103/PhysRevB.101.220404
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