First Observation of Superlattice Reflections in the Hidden Order at 105 K of Spin–Orbit Coupled Iridium Oxide Ca5Ir3O12

Hanate, Hiroki; Hasegawa, Tetsuya; Hayami, Satoru; Tsutsui, Satoshi; Kawano, Shoya; Matsuhira, Kazuyuki

doi:10.7566/jpsj.90.063702

Cited by 23 publications

(6 citation statements)

References 19 publications

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“…Since we have found that the antisymmetric thermopolarization is attributed to the appearance of the ferrotype electric-toroidal dipole order, the compounds with the ferroaxial order for lattice distortions potentially exhibit nonzero antisymmetric thermopolarization. The candidate materials are listed as CaMn 7 O 12 [34], NiTiO 3 [53], RbFe(MoO 4 ) 2 [54], and Ca 5 Ir 3 O 12 [71]. It is desired to search other materials exhibiting electric-toroidal dipole orders in the electronic origin, which might be controllable via the degrees of freedom intrinsic to electrons, such as charge and spin.…”

Section: Discussionmentioning

confidence: 99%

Antisymmetric thermopolarization by electric toroidicity

Nasu

Hayami

2022

Phys. Rev. B

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We investigate electric polarizations that emerge perpendicular to an applied thermal gradient in insulating systems. The thermally induced electric polarization, known as thermopolarization, has been studied conventionally in the case where an electric polarization appears along the thermal gradient. Here, we focus on the antisymmetric component of the thermopolarization tensor, and we reveal that it becomes nonzero due to the ferrotype order for electric-toroidal dipole moments. To describe local electric polarizations originating from the disproportionation of localized electronic clouds, we introduce a two-dimensional three-orbital model with localized s and two p orbitals, where the electric polarization at each site interacts with the neighboring one as dipole-dipole interactions. We find that a vortex-type configuration of local electric polarizations appears as a mean-field ground state, corresponding to a ferrotype electric-toroidal dipole order. By taking account of collective modes from this ordered state, we calculate the coefficient of the thermopolarization based on the linear-response theory. The antisymmetric component is nonzero in the presence of the electric-toroidal dipole order. We clarify that fluctuations in the p orbitals are crucial in enhancing the antisymmetric thermopolarization. We discuss the appearance conditions based on the symmetry argument and the relevance to real materials.

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Section: Discussionmentioning

confidence: 99%

Antisymmetric thermopolarization by electric toroidicity

Nasu

Hayami

2022

Phys. Rev. B

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“…This effect could be observed in the materials with the ferro-type electric-toroidal dipole order. The candidate materials are the compounds with the ferroaxial order for lattice distortions, such as CaMn 7 O 12 [26], NiTiO 3 [45], RbFe(MoO 4 ) 2 [46], and Ca 5 Ir 3 O 12 [61]. It is desired to search other materials exhibiting electric-toroidal dipole orders in the electronic origin, which might be controllable via the degrees of freedom intrinsic to electrons, such as charge and spin.…”

Section: Discussionmentioning

confidence: 99%

Antisymmetric Thermopolarization by Electric Toroidicity

Nasu,

Hayami

2021

Preprint

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We investigate electric polarizations emergent perpendicular to an applied thermal gradient in insulating systems. The thermally-induced electric polarization, known as thermopolarization, has been studied conventionally in the case that an electric polarization appears along the thermal gradient. Here, we focus on the antisymmetric component of the thermopolarization tensor and reveal that it becomes nonzero owing to the ferro-type order for electric-toroidal dipole moments. To describe local electric polarizations originating from the disproportionation of localized electronic clouds, we introduce a two-dimensional three-orbital model with localized s and two p orbitals, where the electric polarization at each site interacts with the neighboring one as dipole-dipole interactions. We find that a vortex-type configuration of local electric polarizations appears as a mean-field ground state, corresponding to a ferro-type electric-toroidal dipole order. By taking account of collective modes from this ordered state, we calculate the coefficient of the thermopolarization based on the linear response theory. The antisymmetric component is nonzero in the presence of the electric-toroidal dipole order. We clarify that fluctuations in the p orbitals are crucial in enhancing the antisymmetric thermopolarization. We discuss the appearance conditions based on the symmetry argument and the relevance to real materials.

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“…90,91) Among them, the atomic multipoles belonging to the E + representation can construct the A + 2 representation corresponding to the ETD within a triangular cluster. Thus, the Hilbert space should include such multipole degrees of freedom belonging to the E + representation to describe the ETD ordering observed in 82) where each triangle unit of the Ir ions is supposed to have the ETD based on the Raman scattering experiments. 80) Based on this symmetry analysis, we consider an effective model to include the multipoles under the E + representation.…”

Section: Mp Rank Basismentioning

confidence: 99%

“…Ca 5 Ir 3 O 12 has a hexagonal structure (P 62m), which might be a prototype to possess both ETD and MTQ, as will be discussed. This material undergoes two phase transitions at 105 K and 7.8 K: 78,79) The former transition was identified as the onset of the ETD ordering with the √ 3a × √ 3a × 3c superstructure in the hexagonal coordinate, [80][81][82] although relevant electronic degrees of freedom for the ETD ordering have been still lacking. The latter was identified as the antiferromagnetic ordering, [83][84][85] where a detailed structure has not been revealed; no magnetic reflections have been observed by powder neutron diffraction experiments 86) and a possibility of multipole magnetic ordering was implied, 85) which is similar to the hidden order in URu 2 Si 2 .…”

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Cluster Toroidal Multipoles Formed by Electric-Quadrupole and Magnetic-Octupole Trimers: A Possible Scenario for Hidden Orders in Ca$_5$Ir$_3$O$_{12}$

Hayami¹,

Tsutsui²,

Hanate³

et al. 2023

Preprint

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Cluster multipole orderings composed of atomic high-rank multipole moments are theoretically investigated with a 5d-electron compound Ca5Ir3O12 in mind. Ca5Ir3O12 exhibits two hidden orders: One is an intermediate-temperature phase with time-reversal symmetry and the other is a low-temperature phase without time-reversal symmetry. By performing the symmetry and augmented multipole analyses for a d-orbital model under the hexagonal point group D 3h , we find that the 120 • -type ordering of the electric quadrupole corresponds to cluster electric toroidal dipole ordering with the electric ferroaxial moment, which can become the microscopic origin of the intermediate-temperature phase in Ca5Ir3O12. Furthermore, based on 193 Ir synchrotron-radiation-based Mössbauer spectroscopy, we propose that the low-temperature phase in Ca5Ir3O12 is regarded as a coexisting state with cluster electric toroidal dipole and cluster magnetic toroidal quadrupole, the latter of which is formed by the 120 • -type ordering of the magnetic octupole and accompanies a small uniform magnetization as a secondary effect. Our results provide a clue to two hidden phases in Ca5Ir3O12.

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First Observation of Superlattice Reflections in the Hidden Order at 105 K of Spin–Orbit Coupled Iridium Oxide Ca₅Ir₃O₁₂

Cited by 23 publications

References 19 publications

Antisymmetric thermopolarization by electric toroidicity

Antisymmetric thermopolarization by electric toroidicity

Antisymmetric Thermopolarization by Electric Toroidicity

Cluster Toroidal Multipoles Formed by Electric-Quadrupole and Magnetic-Octupole Trimers: A Possible Scenario for Hidden Orders in Ca$_5$Ir$_3$O$_{12}$

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