arXiv subjects

M. Tani

Publications and source records attributed to M. Tani.

4 recordsLinked to original sources

arXiv2026

Three-dimensional real-space electron dynamics in graphene driven by strong laser fields

We theoretically investigate the three-dimensional (3D) electron dynamics of graphene in real space under strong laser fields using time-dependent density functional theory (TDDFT). We successfully reproduce the reversal of current direction originating from the cancellation of two oppositely directed residual currents, as previously predicted by Morimoto et al. [Y. Morimoto et al., New J. Phys. 24, 033051 (2022)]. By distinguishing contributions from individual orbitals, our results validate the two-level system approximation and also emphasize that the first-principles approach agrees better with experimental results for light-driven residual current, especially in extremely strong fields. Furthermore, our 3D model reveals that the real-space atomic-scale current induced by strong laser fields is concentrated slightly above and below the graphene basal plane, rather than strictly within it. The two oppositely directed currents exhibit a pronounced height separation in the out-of-plane direction, indicating that the ring current is not confined to the graphene plane but forms a rotating 3D circulation loop which is absent in the reduced-dimensional model.

cond-mat.mes-hall↗

arXiv2021

Noncollinear electro-optic sampling detection of terahertz pulses in a LiNbO$_3$ crystal with avoiding the effect of intrinsic birefringence

We propose and experimentally prove efficient high-resolution electro-optic sampling measurement of broadband terahertz waveforms in a LiNbO$_3$ crystal in the configuration with the probe laser beam propagating along the optical axis of the crystal. This configuration allows one to avoid the detrimental effect of strong intrinsic birefringence of LiNbO$_3$ without any additional optical elements. To achieve velocity matching of the terahertz wave and the probe beam, the terahertz wave is introduced into the crystal through a Si prism at the Cherenkov angle to the probe beam. The workability of the scheme at different wavelengths of the probe optical beam (800 and 1550 nm) is demonstrated.

physics.optics↗

arXiv2015

Constraints on New Gravitylike Forces in the Nanometer Range

We report on a new constraint on gravitylike short-range forces, in which the interaction charge is mass, obtained by measuring the angular distribution of 5 A neutrons scattering off atomic xenon gas. Around 10^7 scattering events were collected at the 40 m small angle neutron scattering beam line located at the HANARO research reactor of the Korean Atomic Energy Research Institute. The extracted coupling strengths of new forces in the Yukawa-type parametrization are g^2 = (0.2 \pm 6.8 \pm 2.0) \times 10^-15 GeV^2 and g^2 = (-5.3 \pm 9.0 + 2.7 -2.8) \times 10^-17 GeV^2 for interaction ranges of 0.1 and 1.0 nm, respectively. These strengths correspond to 95% confidence level limits of g^2 < (1.4 \pm 0.2) \times 10^-14 GeV^-2 and g^2 < (1.3 \pm 0.2) \times 10^-16 GeV^-2, improving the current limits for interaction ranges between 4 and 0.04 nm by a factor of up to 10.

hep-ex↗

arXiv2014

Observation of the Spatial Distribution of Gravitationally Bound Quantum States of Ultracold Neutrons and Its Derivation Using the Wigner Function

Ultracold neutrons (UCNs) can be bound by the potential of terrestrial gravity and a reflecting mirror. The wave function of the bound state has characteristic modulations. We carried out an experiment to observe the vertical distribution of the UCNs above such a mirror at Institut Laue-Langevin in 2011. The observed modulation is in good agreement with that prediction by quantum mechanics using the Wigner function. The spatial resolution of the detector system is estimated to be 0.7 micro meter. This is the first observation of gravitationally bound states of UCNs with submicron spatial resolution.

hep-ex↗