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

Abstract

Continuous quantum phase transitions 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=6.30 GPa, while the lattice symmetry remains in the cubic Fd-3m space group across the quantum critical point. Comparing pressure tuning and the chemical series R2Ir2O7 reveals that the suppression of the AIAO order and the approach to the spin-disordered state is characterized by contrasting evolutions of both the pyrochlore lattice constant a and the trigonal distortion x. The former affects the 5d bandwidth, the latter the Ising anisotropy, and as such 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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Cited by in corpus (7)

• A continuous metal-insulator transition driven by spin correlations
• Role of spin-phonon and electron-phonon interactions in phonon renormalization of (Eu${}_{1-x}$Bi${}_x$)${}_2$Ir${}_2$O${}_7$ across the metal-insulator phase transition: Temperature-dependent Raman and X-ray studies
• Magnetotransport of single crystal Sm${}_2$Ir${}_2$O${}_7$ across the pressure-induced quantum-critical phase boundary
• Structural and spin-glass properties of single crystal $J_{eff}$ = 1/2 pyrochlore antiferromagnet NaCdCo${}_2$F${}_7$ : correlating $T_f$ with magnetic-bond-disorder
• Magnetic order, disorder, and excitations under pressure in the Mott insulator Sr${}_2$IrO${}_4$
• Metal-insulator transitions in pyrochlore oxides
• Three-dimensional checkerboard spin structure on a breathing pyrochlore lattice