Sumio Ishihara

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Graduate Students Rihei Endou, Hiroshi Kohno, Shinichiro Nagahiro (to Jul. 2005), and Daigo Tamura (D3) Masatoshi Mugikura, and Yohei Morii (D2) You Iida, Junya Otsuki, Daichi Kimura, Takayoshi Tanaka, and Jin-Sung Park (from Oct.) (D1) Yohei Iizawa, Akira Uchida, Hiroto Ogawa, Yuji Oyama, Isamu Sakai, Takayuki Sakata, Kenta Sato, Kentaro Sato, Aya Nagano,(More)
The Magnetoelectric (ME) effect in solids is a prominent cross correlation phenomenon, in which the electric field (E) controls the magnetization (M) and the magnetic field (H) controls the electric polarization (P). A rich variety of ME effects and their potential in practical applications have been investigated so far within the transition-metal(More)
Electronic ferroelectricity in molecular organic crystals is reviewed from a theoretical perspective. In particular, we focus on the charge-driven-type electronic ferroelectricity where electronic charge order without inversion symmetry induces a spontaneous electric polarization in quarter-filling systems. Two necessary conditions to realize this type of(More)
We present a theory of ultrafast photoinduced dynamics in a spin-charge coupled system, motivated by pump-probe experiments in perovskite manganites. A microscopic picture for multiple dynamics in spin and charge degrees is examined. Real-time simulations are carried out by two complimentary methods. Our calculation demonstrates that electron motion governs(More)
Dynamical localization, that is, reduction of the intersite electronic transfer integral t by an alternating electric field, E(ω), is a promising strategy for controlling strongly correlated systems with a competing energy balance between t and the Coulomb repulsion energy. Here we describe a charge localization induced by the 9.3 MV cm(-1) instantaneous(More)
Orbital degree of freedom of electrons and its interplay with spin, charge and lattice degrees of freedom are one of the central issues in colossal magnetoresistive manganites. The orbital degree of freedom has until recently remained hidden, since it does not couple directly to most of experimental probes. Development of synchrotron light sources has(More)
Graduate Students Yoshikatsu Hayashi(Research Student), Akira Ishikawa, Alexander Gruneis(to September), Gen’ya Sakurai, Daigo Tamura, Shinichirou Nagahiro, Tomohiko Hatakeyama, and Touichirou Yamamura(D3) Rihei Endou and Hiroshi Kohno (D2) Yuuki Norizoe, Sanae Fujita, Masatoshi Mugikura, and Yohei Morii (D1) You Iida, Akiko Ichikawa, Satoshi Ihara, Hiroshi(More)
A theory of doped perovskite vanadates with spin and orbital orders is presented. Mobile holes are strongly renormalized by spin excitations (magnons) in the spin G-type and orbital C-type (SG-OC) order, and orbital excitations (orbitons) in the spin C-type and orbital G-type (SC-OG) one. Hole dynamics in a staggered t(2g) orbital array is distinguished(More)
In strongly correlated electron systems, enhanced fluctuations in the proximity of the ordered states of electronic degrees of freedom often induce anomalous electronic properties such as unconventional superconductivity. While spin fluctuations in the energy-momentum space have been studied widely using inelastic neutron scattering, other degrees of(More)