Bond Directional Anapole Order in a Spin-Orbit Coupled Mott Insulator Sr_{2}(Ir_{1-x}Rh_{x})O_{4}

Bond Directional Anapole Order in a Spin-Orbit Coupled Mott Insulator Sr_{2}(Ir_{1-x}Rh_{x})O_{4}

An anapole state that breaks inversion and time-reversal symmetries while preserving translation symmetry of an underlying lattice has aroused great interest as a new quantum state, but only a few candidate materials have been reported. Recently, in a spin-orbit coupled Mott insulator Sr_{2}(Ir_{1-x...

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Autores principales: H. Murayama, K. Ishida, R. Kurihara, T. Ono, Y. Sato, Y. Kasahara, H. Watanabe, Y. Yanase, G. Cao, Y. Mizukami, T. Shibauchi, Y. Matsuda, S. Kasahara
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Publicado: American Physical Society 2021
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QC1-999
Acceso en línea:https://doaj.org/article/3b7aefc3dfd04f2998f39fdaa2564f26
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spelling oai:doaj.org-article:3b7aefc3dfd04f2998f39fdaa2564f262021-12-02T14:24:38ZBond Directional Anapole Order in a Spin-Orbit Coupled Mott Insulator Sr_{2}(Ir_{1-x}Rh_{x})O_{4}10.1103/PhysRevX.11.0110212160-3308https://doaj.org/article/3b7aefc3dfd04f2998f39fdaa2564f262021-02-01T00:00:00Zhttp://doi.org/10.1103/PhysRevX.11.011021http://doi.org/10.1103/PhysRevX.11.011021https://doaj.org/toc/2160-3308An anapole state that breaks inversion and time-reversal symmetries while preserving translation symmetry of an underlying lattice has aroused great interest as a new quantum state, but only a few candidate materials have been reported. Recently, in a spin-orbit coupled Mott insulator Sr_{2}(Ir_{1-x}Rh_{x})O_{4}, the emergence of a possible hidden-order phase with broken inversion symmetry has been suggested at T_{Ω} above the Néel temperature by optical second-harmonic-generation measurements. Moreover, polarized neutron diffraction measurements revealed broken time-reversal symmetry below T_{Ω}, which was supported by subsequent muon spin relaxation experiments. However, the nature of this mysterious phase remains largely elusive. Here, we investigate the hidden-order phase through the combined measurements of the in-plane magnetic anisotropy with exceptionally high-precision magnetic torque and the nematic susceptibility with elastoresistance. A distinct twofold in-plane magnetic anisotropy along the [110] Ir-O-Ir bond direction sets in below about T_{Ω}, providing thermodynamic evidence for a nematic phase transition with broken C_{4} rotational symmetry. However, in contrast to the even-parity nematic transition reported in other correlated electron systems, the nematic susceptibility exhibits no divergent behavior towards T_{Ω}. These results provide bulk evidence for an odd-parity order parameter with broken rotational symmetry in the hidden-order state. We discuss the hidden order in terms of an anapole state, in which the polar toroidal moment is induced by two current loops in each IrO_{6} octahedron of opposite chirality. Contrary to the simplest loop-current pattern previously suggested, the present results are consistent with a pattern in which the intra-unit cell loop current flows along only one of the diagonal directions in the IrO_{4} square.H. MurayamaK. IshidaR. KuriharaT. OnoY. SatoY. KasaharaH. WatanabeY. YanaseG. CaoY. MizukamiT. ShibauchiY. MatsudaS. KasaharaAmerican Physical SocietyarticlePhysicsQC1-999ENPhysical Review X, Vol 11, Iss 1, p 011021 (2021)
institution DOAJ
collection DOAJ
language EN
topic Physics
QC1-999
spellingShingle Physics
QC1-999
H. Murayama
K. Ishida
R. Kurihara
T. Ono
Y. Sato
Y. Kasahara
H. Watanabe
Y. Yanase
G. Cao
Y. Mizukami
T. Shibauchi
Y. Matsuda
S. Kasahara
Bond Directional Anapole Order in a Spin-Orbit Coupled Mott Insulator Sr_{2}(Ir_{1-x}Rh_{x})O_{4}
description An anapole state that breaks inversion and time-reversal symmetries while preserving translation symmetry of an underlying lattice has aroused great interest as a new quantum state, but only a few candidate materials have been reported. Recently, in a spin-orbit coupled Mott insulator Sr_{2}(Ir_{1-x}Rh_{x})O_{4}, the emergence of a possible hidden-order phase with broken inversion symmetry has been suggested at T_{Ω} above the Néel temperature by optical second-harmonic-generation measurements. Moreover, polarized neutron diffraction measurements revealed broken time-reversal symmetry below T_{Ω}, which was supported by subsequent muon spin relaxation experiments. However, the nature of this mysterious phase remains largely elusive. Here, we investigate the hidden-order phase through the combined measurements of the in-plane magnetic anisotropy with exceptionally high-precision magnetic torque and the nematic susceptibility with elastoresistance. A distinct twofold in-plane magnetic anisotropy along the [110] Ir-O-Ir bond direction sets in below about T_{Ω}, providing thermodynamic evidence for a nematic phase transition with broken C_{4} rotational symmetry. However, in contrast to the even-parity nematic transition reported in other correlated electron systems, the nematic susceptibility exhibits no divergent behavior towards T_{Ω}. These results provide bulk evidence for an odd-parity order parameter with broken rotational symmetry in the hidden-order state. We discuss the hidden order in terms of an anapole state, in which the polar toroidal moment is induced by two current loops in each IrO_{6} octahedron of opposite chirality. Contrary to the simplest loop-current pattern previously suggested, the present results are consistent with a pattern in which the intra-unit cell loop current flows along only one of the diagonal directions in the IrO_{4} square.
format article
author H. Murayama
K. Ishida
R. Kurihara
T. Ono
Y. Sato
Y. Kasahara
H. Watanabe
Y. Yanase
G. Cao
Y. Mizukami
T. Shibauchi
Y. Matsuda
S. Kasahara
author_facet H. Murayama
K. Ishida
R. Kurihara
T. Ono
Y. Sato
Y. Kasahara
H. Watanabe
Y. Yanase
G. Cao
Y. Mizukami
T. Shibauchi
Y. Matsuda
S. Kasahara
author_sort H. Murayama
title Bond Directional Anapole Order in a Spin-Orbit Coupled Mott Insulator Sr_{2}(Ir_{1-x}Rh_{x})O_{4}
title_short Bond Directional Anapole Order in a Spin-Orbit Coupled Mott Insulator Sr_{2}(Ir_{1-x}Rh_{x})O_{4}
title_full Bond Directional Anapole Order in a Spin-Orbit Coupled Mott Insulator Sr_{2}(Ir_{1-x}Rh_{x})O_{4}
title_fullStr Bond Directional Anapole Order in a Spin-Orbit Coupled Mott Insulator Sr_{2}(Ir_{1-x}Rh_{x})O_{4}
title_full_unstemmed Bond Directional Anapole Order in a Spin-Orbit Coupled Mott Insulator Sr_{2}(Ir_{1-x}Rh_{x})O_{4}
title_sort bond directional anapole order in a spin-orbit coupled mott insulator sr_{2}(ir_{1-x}rh_{x})o_{4}
publisher American Physical Society
publishDate 2021
url https://doaj.org/article/3b7aefc3dfd04f2998f39fdaa2564f26
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