Electric Ferro-Axial Moment as Nanometric Rotator and Source of Longitudinal Spin Current

Hayami, Satoru; Oiwa, Rikuto; Kusunose, Hiroaki

doi:10.48550/arxiv.2111.10519

Cited by 4 publications

(7 citation statements)

References 37 publications

(45 reference statements)

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“…where l is the orbital angular momentum operator for the p orbital [42]. The expression of G (a) z in Eq.…”

Section: B Single-site Systemmentioning

confidence: 99%

“…In this sense, the ferroaxial moment is not directly coupled to the electromagnetic fields. Meanwhile, such a ferroaxial property has recently attracted much attention, since it leads to unconventional off-diagonal responses, such as the spin-current generation [42,43] and antisymmetric thermopolarization [44], in the context of the electric toroidal moment. As the ferroaxial moment can be present in the 13 crystallographic point groups without vertical mirror symmetry, C 6h , C 6 , C 3h , C 4h , C 4 , S 4 , C 3i , C 3 , C 2h , C 2 , C s , C i , and C 1 , a variety of materials are expected to exhibit the ferroaxial physics.…”

Section: Introductionmentioning

confidence: 99%

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Ferroaxial moment induced by vortex spin texture

Hayami

2022

Phys. Rev. B

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The nature of an electric ferroaxial moment characterizing a time-reversal-even axial-vector quantity is theoretically investigated under magnetic orderings. We clarify that a vortex spin texture results in the emergence of the ferroaxial moment depending on the helicity. By introducing a multipole description, we show that the ferroaxial nature appears when two types of odd-parity magnetic multipoles become active under the vortex spin texture: One is the magnetic monopole and the other is the magnetic toroidal dipole. We present all the magnetic point groups to possess the ferroaxial moment in the presence of the magnetic orderings with the magnetic monopole and magnetic toroidal dipole. Moreover, we specifically consider a multiorbital model in a four-sublattice tetragonal system to demonstrate the ferroaxial moment induced by the vortex spin texture. We show that the ferroaxial moment is microscopically characterized by both the cluster-scale and atomic-scale axial-vector quantities: The former is described by the vortex of the local electric dipole and the latter is represented by the outer product of the local orbital and spin angular momenta. Moreover, we find that the atomic spin-orbit coupling and the hybridization between orbitals with different parity are key ingredients to induce the ferroaxial moment. We also apply the result to a magnetic skyrmion with a topologically nontrivial spin texture and discuss candidate materials.

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“…where l is the orbital angular momentum operator for the p orbital [42]. The expression of G (a) z in Eq.…”

Section: B Single-site Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ferroaxial moment induced by vortex spin texture

Hayami

2022

Phys. Rev. B

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“…Nonetheless, an electronic order involving the electric-toroidal dipoles, simpler than the quadrupole ones, remains elusive. This is because the dipole component is both spatial and time-reversal parity-even, complicating its experimental observation, while the longitudinal dissipationless spin-current generation was proposed recently, originating from electric-toroidal octupoles [52].…”

Section: Introductionmentioning

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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“…Nonetheless, an electronic order involving the electric-toroidal dipoles, simpler than the quadrupole ones, remains elusive. This is because the dipole component is both spatial and time-reversal parity even, complicating its experimental observation while the longitudinal dissipationless spin-current generation was proposed recently, originating from electric-toroidal octupoles [44].…”

Section: Introductionmentioning

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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Electric Ferro-Axial Moment as Nanometric Rotator and Source of Longitudinal Spin Current

Cited by 4 publications

References 37 publications

Ferroaxial moment induced by vortex spin texture

Ferroaxial moment induced by vortex spin texture

Antisymmetric thermopolarization by electric toroidicity

Antisymmetric Thermopolarization by Electric Toroidicity

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