A5041791519- Multiferroics and related materials
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Topological Materials and Phenomena
- Organic and Molecular Conductors Research
- Magneto-Optical Properties and Applications
- Solid-state spectroscopy and crystallography
- Magnetism in coordination complexes
- Advanced Chemical Physics Studies
- Graphene research and applications
- Magnetic properties of thin films
- Molecular Junctions and Nanostructures
- Nuclear physics research studies
- Perovskite Materials and Applications
- 2D Materials and Applications
- Electronic and Structural Properties of Oxides
- Ferroelectric and Piezoelectric Materials
- Quantum and electron transport phenomena
- Silicon Nanostructures and Photoluminescence
- Quantum Chromodynamics and Particle Interactions
- Semiconductor Quantum Structures and Devices
- Physics of Superconductivity and Magnetism
- Terahertz technology and applications
- Advanced NMR Techniques and Applications
- Spectroscopy and Quantum Chemical Studies
RIKEN Center for Emergent Matter Science
2015-2025
The University of Tokyo
2015-2025
Japan Science and Technology Agency
2008-2018
Osaka University
2001-2013
Tohoku University
1998
Kumamoto University
1997
IBM Research - Tokyo
1991
Nihon University
1981
Abstract Electrodynamic responses from three-dimensional topological insulators are characterized by the universal magnetoelectric term constituent of Lagrangian formalism. The quantized coupling, which is generally referred to as effect, has been predicted induce exotic phenomena including low-energy magneto-optical effects. Here we report experimental indication exemplified Faraday and Kerr rotations in quantum anomalous Hall states magnetic insulator surfaces terahertz magneto-optics....
Abstract The Weyl semimetal (WSM), which hosts pairs of points and accompanying Berry curvature in momentum space near Fermi level, is expected to exhibit novel electromagnetic phenomena. Although the large optical/electronic responses such as nonlinear optical effects intrinsic anomalous Hall effect (AHE) have recently been demonstrated indeed, conclusive evidence for their topological origins has remained elusive. Here, we report gigantic magneto-optical (MO) response arising from...
We have spectroscopically investigated the thermally and doping-induced metal-insulator transitions for pyrochlore-type ${\mathrm{Nd}}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$ as well its Rh-doped analogs ${\mathrm{Nd}}_{2}({\mathrm{Ir}}_{1\ensuremath{-}x}{\mathrm{Rh}}_{x}{)}_{2}{\mathrm{O}}_{7}$, where spin-orbit interaction electron correlation is effectively tuned by doping level ($x$). The charge dynamics dramatically changes on an energy scale of 1 eV in course transitions, while...
Temperature (5--250 K) and magnetic-field (0--70 kOe) variations of the low-energy (1--10 meV) electrodynamics spin excitations have been investigated for a complete set light-polarization configurations ferroelectric magnet ${\text{DyMnO}}_{3}$ by using terahertz time-domain spectroscopy. We identify pronounced absorption continuum (1--8 with peak feature around 2 meV, which is electric-dipole active only light $E$ vector along $a$ axis. This band grows in intensity lowering temperature...
The wide range optical spectra on a multiferroic prototype ${\mathrm{TbMnO}}_{3}$ have been investigated to clarify the origin of spin excitations observed in far-infrared region. We elucidate full band structure, whose high energy edge ($133\text{ }\text{ }{\mathrm{cm}}^{\ensuremath{-}1}$) exactly corresponds twice highest-lying magnon energy. Thus this absorption is clearly assigned two-magnon excitation driven by electric field light. There an overlap between and phonon ranges, where...
Magnetically-driven ferroelectric atomic displacements of the order 10$^{-3} Angstrom have been observed in orthorhombic (perovskite like) YMnO$_3$ by a single-crystal synchrotron x-ray diffraction. The refined polar structure shows characteristic bond alternation driven exchange striction staggered Mn-O-Mn arrays with $\uparrow\uparrow\downarrow\downarrow$ type ordering, giving rise to spontaneous polarization along a-axis. First-principles calculations based on Berry phase method as well...
Recent spectroscopic studies at terahertz frequencies for a variety of multiferroics endowed with both ferroelectric and magnetic orders have revealed the possible emergence new collective excitation, frequently referred to as electromagnon. It is in origin, but it becomes active response electric field component light. Here we give an overview our recent advance time-domain spectroscopy electromagnons, or electric-dipole resonances, focused on perovskite manganites—RMnO3 (R denotes...
We have investigated the charge transport and low-energy dynamics originating from antiferromagnetic (AF) domain wall (DW) in pyrochlore-type Nd${}_{2}$Ir${}_{2}$O${}_{7}$ with all-in all-out type AF ground state by means of magneto-resistance measurement terahertz time-domain spectroscopy. The resistivity is much lower multi-magnetic-domain than nearly single-magnetic-domain one. Furthermore, optical conductivity spectrum unravels a Drude-like response only multidomain state; absorption...
Both electric- and magnetic-dipole active spin excitations, i.e., electromagnons, which mediate the dynamical magnetoelectric effect, have been investigated for a multiferroic perovskite of manganite by optical spectroscopy at terahertz frequencies. Upon resonance 1 meV in phase with $bc$-plane cycloidal order, gigantic effect has observed as nonreciprocal directional dichroism or birefringence. The light $k$-vector-dependent difference...
The vector analyzing power has been measured for the elastic scattering of neutron-rich 6He from polarized protons at 71 MeV/nucleon making use a newly constructed solid proton target operated in low magnetic field and high temperature. Two approaches based on local one-body potentials were applied to investigate spin-orbit interaction between nucleus. An optical model analysis revealed that potential is characterized by shallow long-ranged shape compared with global systematics stable...
We report the polarization rotation of terahertz light resonant with magnetoelectric (ME) spin excitation in multiferroic (Fe,Zn)_{2}Mo_{3}O_{8}. This resonance reflects frequency dispersion diagonal ME susceptibility (axion term), which we quantitatively reproduce thermal and magnetic-field evolution observed spectra. The application sum rule on extrapolated dc value spectral weight oscillator provides insight into linear effect. present finding highlights a novel optical functionality...
Controlling the chiral degree of freedom in matter has long been an important issue for many fields science. The spin-spiral order, which exhibits a strong magnetoelectric coupling, gives rise to chirality irrespective atomic arrangement matter. Here, we report resonantly enhanced natural optical activity on electrically active magnetic excitation, that is, electromagnon, multiferroic cupric oxide. electric field control is demonstrated through magnetically induced endowed with coupling....
Abstract The magnetic skyrmion is a spin-swirling topological object characterized by its nontrivial winding number, holding potential for next-generation spintronic devices. While optical readout has become increasingly important towards the high integration and ultrafast operation of those devices, response skyrmions remained elusive. Here, we show magneto-optical Kerr effect (MOKE) induced formation, i.e., MOKE, in Gd 2 PdSi 3 . significantly enhanced rotation found phase demonstrates...
The electronic structure of compensated antiferromagnets (CAF) creates large functional responses, reminiscent ferromagnets and suitable for data storage readout, despite (nearly) net-zero spontaneous magnetization. Many experimental signatures CAF - such as giant thermoelectric Nernst effects should be enhanced when two or more bands are nearly degenerate in vicinity the Fermi energy. Here, we report a zero-field, effect >1 μV/K CoNb3S6 its tiny net magnetization ~2 milli − μB. As drivers...
Spectral blue shift of excitonic transition due to quantum confinement in Si0.84Ge0.16/Si strained-layer wells, grown by gas-source Si molecular beam epitaxy, is reported. Intense photoluminescence was observed at elevated temperatures though reduced intensity the thermalization holes barriers.
Vector analyzing power for the proton-He6 elastic scattering at 71 MeV/nucleon has been measured first time, with a newly developed polarized proton solid target, which works low magnetic field of 0.09 T. The results are found to be incompatible t-matrix folding model prediction. Comparisons data g-matrix analyses clearly show that vector is sensitive nuclear structure used in reaction analysis. α-core distribution He6 suggested possible key understanding sensitivity.Received 27 May...
Magnetic excitations are investigated for a hexagonal polar magnet Fe2Mo3O8 by terahertz spectroscopy. We observed magnon modes including an electric-field active magnon, electromagnon, in the collinear antiferromagnetic phase with spins parallel to c axis. unravel nature of these investigating correlation between evolution mode profile and magnetic transition from ferrimagnetic order induced field or Zn-doping. propose that electromagnon involves collective precession oscillating in-plane...
SignificanceThe quantum-mechanical geometric phase of electrons provides various phenomena such as the dissipationless photocurrent generation through shift current mechanism. So far, generations are limited to above or near band-gap photon energy, which contradicts increasing demand low-energy photonic functionality. We demonstrate optical phonon excitations in ferroelectric BaTiO3 by using terahertz light with energy far below band gap. This without electron-hole pair is never explained...
Abstract Poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is a prototypical conducting polymer. When polar solvent used during film fabrication, the hole-doped PEDOT oligomers form crystalline clusters in films, exhibiting high conductivity. However, whether hole carriers exhibit band transport has not been clarified yet. Here, we employ multilayer spin-coating method using an aqueous solution with ethylene glycol, additional procedures of dipping films glycol or dropping...
Electromagnon, magnetic excitation driven by an electric field of light, has been investigated for a series perovskite manganites $R{\text{MnO}}_{3}$. Two distinct excitations commonly appear in the spiral spin-ordered state, and systematic changes their peak positions spectral weights were observed as function radius $R$-ion or equivalently spin-exchange interaction energies. By comparing results with spin-wave calculation based on Heisenberg model, higher-lying is assigned to zone-edge...