arXiv subjects

Atsushi Ono

Publications and source records attributed to Atsushi Ono.

22 records · Page 2Linked to original sources

arXiv2018

Photocontrol of magnetic structure in an itinerant magnet

We study the photoinduced magnetic transition in an itinerant magnet described by the double-exchange model, in which conduction electrons couple with localized spins through the ferromagnetic (FM) Hund coupling. It is shown that intense light applied to the FM ground state induces an antiferromagnetic (AFM) order, in contrast to the AFM-to-FM transition due to the photocarrier injection. In particular, we focus on the mechanism for instability of the FM structure by the light irradiation. The magnon spectrum in the Floquet state is formulated on the basis of the pertrubative expansion of the Floquet Green function. The magnon dispersion shows softening at momentum $(π,π)$ in the square lattice with increasing the light amplitude, implying photoinduced AFM instability. This result is mainly attributed to a nonequilibrium electron distribution, which promotes low-energy Stoner excitations. The transient optical conductivity spectra characterized by interband excitations and Floquet sidepeaks are available to identify the photoinduced AFM state.

cond-mat.str-el↗

arXiv2017

Double-Exchange Interaction in Optically Induced Nonequilibrium State: A Conversion from Ferromagnetic to Antiferromagnetic Structure

The double-exchange (DE) interaction, that is, a ferromagnetic (FM) interaction due to a combination of electron motion and the Hund coupling, is a well known source of a wide class of FM orders. Here, we show that the DE interaction in highly photoexcited states is antiferromagnetic (AFM). Transient dynamics of quantum electrons coupled with classical spins are analyzed. An ac field applied to a metallic FM state results in an almost perfect Néel state. A time characterizing the FM-to-AFM conversion is scaled by light amplitude and frequency. This hidden AFM interaction is attributable to the electron-spin coupling under nonequilibrium electron distribution.

cond-mat.str-el↗

arXiv2016

Optical suppression of electron motion in low-dimensional correlated electron system

Suppression of electron motion under an alternating current (AC) electric field is examined in a one-dimensional Hubbard model. Utilizing three complementary calculation methods, it is found unambiguously that magnitudes of the kinetic-energy suppressions are influenced sensitively by the Coulomb interaction as well as the electron density. The phase and frequency in the AC field do not bring about major effects. The results are interpreted as a combined effect of the Coulomb interaction and the AC field, and provide a guiding principle for the photocontrol of correlated electron motion.

cond-mat.str-el↗

arXiv2016

Pulse excitation to continuous-wave excitation in a low-dimensional interacting quantum system

Real-time dynamics in one-dimensional transverse Ising model coupled with the time-dependent oscillating field is analyzed by using the infinite time-evolving block decimation algorithm and the Floquet theory. In particular, the transient dynamics induced by the pulse field and their connections to the dynamics by a continuous-wave field are focused on. During the pulse-field irradiation, the order parameter shows a characteristic oscillation, in which the frequency shifts from the pulse-field frequency. This is considered as a kind of the Rabi oscillation, but the frequency strongly depends on the intersite Ising interaction. After turning off the pulse field, the oscillation remains with a frequency $\mathitΩ$ and a damping constant $γ$. In the case of low fluence, both $\mathitΩ$ and $γ$ are scaled by the pulse amplitude in a wide range of the parameter values of the model. In the case of high fluence, $\mathitΩ$ and $γ$ are arranged by a product of the pulse amplitude and the pulse width. This implies that the dynamics after turning off the pulse field are decided by a population of the excited state when the pulse field is turned off.

cond-mat.str-el↗