Yoshiaki Sekine

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We demonstrate the time reversal Aharonov-Casher (AC) effect in small arrays of mesoscopic semiconductor rings. By using an electrostatic gate we can control the spin precession rate and follow the AC phase over several interference periods. We show that we control the precession rate in two different gate voltage ranges; in the lower range the gate voltage(More)
We report nonlinear terahertz transmission through photoexcited graphene using optical-pump/terahertz-probe technique. Transient enhancement in the terahertz transmission of the graphene sample is observed when the sample is photoexcited. This transmission enhancement is found to decrease nonlinearly with the terahertz electric field.
A novel millimeter-wave leaky-wave antenna is described which consists of a dielectric slab loaded by metallic strips periodically. By applying several new techniques to reduce conductor loss of the ground plane and to suppress the reflections in the dielectric waveguide due to the metallic strips, we achieved a very high antenna efficiency, exceeding 70%(More)
Terahertz field-induced transmission enhancement in monolayer epitaxial graphene is observed with increasing terahertz field. Photoexcitation leads to further transmission enhancement that is found to be less for the higher terahertz field amplitudes.
Raman spectroscopy has been used in chemistry and physics to investigate the fundamental process involving light and phonons. The carbon nanohorn introduces a new subject to Raman spectroscopy, namely topology. We show theoretically that a photoexcited carrier with a nonzero winding number activates a topological D Raman band through the Aharonov-Bohm(More)
The Rashba spin-orbit interaction in InGaAs quantum wells (QW) is studied using the weak anti-localization analysis as a function of the structural inversion asymmetry (STA). A clear cross-over from positive to negative magnetoresistance near zero-magnetic field is observed by controlling the degree of the SIA in the QWs. This is a strong evidence of a(More)
We recently determined the values of intrinsic spin-orbit (SO) parameters for In0.52Al0.48As/In0.53Ga0.47As(10 nm)/In0.52Al0.48As (InGaAs/InAlAs) quantum wells (QW), lattice-matched to (001) InP, from the weak localization/antilocalization analysis of the low-temperature magneto-conductivity measurements [1]. We have then studied the subband energy spectra(More)
We have observed the well-kown quantum Hall effect (QHE) in epitaxial graphene grown on silicon carbide (SiC) by using, for the first time, only commercial NdFeB permanent magnets at low temperature. The relatively large and homogeneous magnetic field generated by the magnets, together with the high quality of the epitaxial graphene films, enables the(More)
We report a novel etchant-free transfer method of graphene using the intercalation of alkanethiol self-assembled monolayers (SAMs) at the graphene/Cu interfaces. The early stage of intercalation proceeds through graphene grain boundaries or defects within a few seconds at room temperature until stable SAMs are formed after a few hours. The formation of SAMs(More)