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Magnetization induced by a nonlinear response to temperature gradient in , and altermagnets
Motohiko Ezawa
It is a highly nontrivial question whether magnetization is induced by a nonlinear response to a temperature gradient in systems where the linear response is forbidden by inversion…
Fourth-order and six-order nonlinear spin current rectifier in three-dimensional -wave and -wave odd-parity magnet
Motohiko Ezawa
Higher-order symmetric -wave magnets consist of two groups. One includes -wave, -wave and -wave altermagnets, while the other includes -wave and -wave odd-parity…
Spin-selective elliptic optical dichroism and perfectly spin-polarized third-order nonlinear photocurrent in altermagnets
Motohiko Ezawa
We show that the low-energy theory of a -wave altermagnet is characterized by anisotropic Dirac cones with spin-split band structures based on a recently proposed tight-binding…
Nonlinear spin-Seebeck diode in -wave magnets, third-order spin-Nernst effects in -wave magnets and spin-Nernst effects in -wave altermagnets
Motohiko Ezawa
A prominent feature of -wave altermagnets is that spin current is generated by applying temperature gradient, which is known as the spin-Nernst effect. We show in -wave magne…
Quantum geometry and -wave magnets with
Motohiko Ezawa
Quantum geometry is a differential geometry based on quantum mechanics. It is related to various transport and optical properties in condensed matter physics. The Zeeman quantum ge…
Almost half-quantized planar Hall effects in -wave magnets with
Motohiko Ezawa
The planar Hall effect is a phenomenon that the Hall conductivity emerges perpendicular to the electric field in the presence of an in-plane magnetic field. We investigate the plan…
Higher-order bulk photovoltaic effects, quantum geometry and application to -wave magnets
Motohiko Ezawa
The injection and shift currents are generalized to the th-order injection and shift currents for the longitudinal conductivities in the two-band model, where is the…
Quantum geometry and elliptic optical dichroism in -wave magnets
Motohiko Ezawa
The quantum geometric tensor is composed of the Berry curvature and the quantum metric, which is observable by means of optical absorption of elliptically polarized light. Especial…
Out-of-plane Edelstein effects: Electric-field induced magnetization in -wave magnets
Motohiko Ezawa
In-plane magnetization is induced by the Edelstein effect in the Rashba spin-orbit interaction system. However, out-of-plane magnetization is more useful for switching a ferromagne…
Bulk photovoltaic effects in altermagnets
Motohiko Ezawa
The bulk photovoltaic effect is a photocurrent generation from alternating electric field, which is a promising candidate for future efficient solar cell technology. It is the seco…
Realization of a one-dimensional topological insulator in ultrathin germanene nanoribbons
Dennis J. Klaassen, Lumen A. G. Eek, Alexander N. Rudenko +9
Realizing a one-dimensional (1D) topological insulator and identifying the lower dimensional limit of two-dimensional (2D) behavior are crucial steps toward developing high-density…
Third-order and fifth-order nonlinear spin-current generation in -wave and -wave altermagnets, and perfectly nonreciprocal spin-current in -wave magnets
Motohiko Ezawa
A prominent feature of -wave altermagnets is the pure spin current generated in the absence of spin-orbit interactions. In the context of symmetry, there are the -wave, the $…
Purely electrical detection of the spin-splitting vector in -wave magnets based on linear and nonlinear conductivities
Motohiko Ezawa
A -wave magnet has a momentum-dependent spin splitting and zero-net magnetization just as in the case of an altermagnet. It will be useful for high-density and ultra-fast memory…
Intrinsic nonlinear conductivity induced by quantum geometry in altermagnets and measurement of the in-plane Néel vector
Motohiko Ezawa
The -component of the Néel vector is measurable by the anomalous Hall conductivity in altermagnets because time reversal symmetry is broken. On the other hand, it is a nontrivia…
Analytic approach to quantum metric and optical conductivity in Dirac models with parabolic mass in arbitrary dimensions
Motohiko Ezawa
The imaginary part of the quantum geometric tensor is the Berry curvature, while the real part is the quantum metric. Dirac fermions derived from a tight-binding model naturally co…
Topological Corner States in Bilayer and Trilayer Systems with Vertically Stacked Topological Heterostructures
Natsuko Ishida, Motohiko Ezawa, Guangtai Lu +4
We investigate bilayer and trilayer systems composed of topologically distinct, vertically stacked layers, forming topological heterostructures based on the Benalcazar-Bernevig-Hug…
Topological insulators and superconductors based on -wave magnets,electrical control and detection of a domain wall
Motohiko Ezawa
Altermagnets are time-reversal broken antiferromagnets, where the component of the Néel vector is detectable by anomalous Hall effects. On the other hand, recently proposed …
Moiré-modulated band gap and van Hove singularities in twisted bilayer germanene
Pantelis Bampoulis, Carolien Castenmiller, Dennis J. Klaassen +4
Twisting bilayers of two-dimensional topological insulators has the potential to create unique quantum states of matter. Here, we successfully synthesized a twisted bilayer of germ…
Detecting the Néel vector of altermagnet by attaching a topological insulator and crystalline valley-edge insulator
Motohiko Ezawa
In order to detect the Néel vector of an altermagnet, we investigate topological phases in a bilayer system composed of an altermagnet and a two-dimensional topological insulator d…
Transition from topological to chaos in the nonlinear Su-Schrieffer-Heeger model
Kazuki Sone, Motohiko Ezawa, Zongping Gong +3
Recent studies on topological materials are expanding into the nonlinear regime, while the central principle, namely the bulk-edge correspondence, is yet to be elucidated in the st…
Nonadiabatic nonlinear non-Hermitian quantized pumping
Motohiko Ezawa, Natsuko Ishida, Yasutomo Ota +1
We analyze a quantized pumping in a nonlinear non-Hermitian photonic system with nonadiabatic driving. The photonic system is made of a waveguide array, where the distances between…
Cavity-induced topological edge and corner states
Motohiko Ezawa
We investigate a two-level system with alternating XX coupling in a photon cavity. It is mapped to a free boson model equally coupled to a photon, whose interaction is highly nonlo…
Chiral Skyrmions Interacting with Chiral Flowers
Xichao Zhang, Jing Xia, Oleg A. Tretiakov +5
The chiral nature of active matter plays an important role in the dynamics of active matter interacting with chiral structures. Skyrmions are chiral objects, and their interactions…
Universal quantum computing based on magnetic domain wall qubits
Shuang Li, Xichao Zhang, Motohiko Ezawa +1
Quantum computers allow to solve efficiently certain problems that are intractable for classical computers. For the realization of a quantum computer, a qubit design as the basic b…