Tomohiro Yokoyama

ORCID: 0000-0002-9192-0165
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About
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Research Areas
  • Quantum and electron transport phenomena
  • Physics of Superconductivity and Magnetism
  • Microgrid Control and Optimization
  • Multilevel Inverters and Converters
  • Topological Materials and Phenomena
  • Mechanical and Optical Resonators
  • Magnetic properties of thin films
  • Plasmonic and Surface Plasmon Research
  • Advanced DC-DC Converters
  • Gold and Silver Nanoparticles Synthesis and Applications
  • Orbital Angular Momentum in Optics
  • Semiconductor Quantum Structures and Devices
  • Near-Field Optical Microscopy
  • Transactional Analysis in Psychotherapy
  • Atomic and Subatomic Physics Research
  • Photonic and Optical Devices
  • Surface and Thin Film Phenomena
  • Cold Atom Physics and Bose-Einstein Condensates
  • Advancements in Semiconductor Devices and Circuit Design
  • Quantum Dots Synthesis And Properties
  • Child Therapy and Development
  • Microfluidic and Bio-sensing Technologies
  • Cellular and Composite Structures
  • Psychotherapy Techniques and Applications
  • Quantum optics and atomic interactions

Niigata University
2024-2025

Osaka University
2004-2025

Tokushima University
2018-2024

Toyota Motor Corporation (Japan)
2024

Tokyo Denki University
2003-2023

Shibaura Institute of Technology
2023

Tohoku University
2017-2021

Toyohashi University of Technology
2017-2018

Delft University of Technology
2014-2017

The University of Tokyo
2017

We investigate theoretically the Josephson junction of semiconductor nanowire with strong spin-orbit (SO) interaction in presence magnetic field. By using a tight-binding model, energy levels $E_n$ Andreev bound states are numerically calculated as function phase difference $\varphi$ between two superconductors case short junctions. The DC current is evaluated from levels. In absence SO interaction, $0$-$\pi$ transition due to field clearly observed. coexistence and Zeeman effect results...

10.1103/physrevb.89.195407 article EN Physical Review B 2014-05-08

The energies of Andreev bound states (ABS) forming in an $N$-terminal junction are affected by $N\ensuremath{-}1$ independent macroscopic phase differences between superconducting leads and can be regarded as energy bands $(N\ensuremath{-}1)$-periodic solids owing to the $2\ensuremath{\pi}$ periodicity all phases. We investigate singularities peculiarities resulting ABS spectrum combining phenomenological analytical methods illustrating with numerical results. pay special attention...

10.1103/physrevb.92.155437 article EN Physical Review B 2015-10-30

The Josephson junction (JJ) is an essential element of superconducting (SC) devices for both fundamental and applied physics. short-range coherent coupling two adjacent JJs forms Andreev molecule states (AMSs), which provide a new ingredient to engineer exotic SC phenomena such as topological qubits. Here we tunneling spectroscopy measurements on device consisting electrically controllable planar sharing single electrode. We discover that spectra in the coupled JJ are highly modulated from...

10.1038/s41467-023-44111-3 article EN cc-by Nature Communications 2023-12-13

Modal strong coupling between localized surface plasmon resonance and a Fabry-Pérot nanocavity has been studied to improve the quantum efficiency of artificial photosynthesis. In this research, we employed Au nanodisk/titanium dioxide/Au film modal structures investigate mechanism enhancement. We found that coherence within enhances apparent hot-electron injection from nanodisks titanium dioxide layer. Under near-field mapping using photoemission electron microscopy, existence was directly...

10.1021/acsnano.2c12670 article EN cc-by-nc-nd ACS Nano 2023-04-21

A Josephson junction (JJ) is a key device for developing superconducting circuits, wherein supercurrent in the JJ controlled by phase difference between two electrodes. When JJs sharing one electrode are coherently coupled and form Andreev molecules, of expected to be nonlocally another JJ. Here, we evaluate as function local nonlocal differences. Consequently, results exhibit that control generates finite even when zero. In addition, an offset giving ground state depends on difference....

10.1126/sciadv.adj3698 article EN cc-by-nc Science Advances 2023-12-13

ABSTRACT This research developed a complex capacitance sensor using quartz oscillator for non‐invasively imaging of rebars position in reinforced concrete structures. The use different electrode structures and floating located on the backside allowed control sensing depth. technology is expected to realize simpler maintenance management process infrastructure quality.

10.1002/ecj.12483 article EN Electronics and Communications in Japan 2025-01-02

Abstract Plasmonic nanocavities with highly localized fields in their nanogaps significantly enhance light–matter interactions at the nanoscale, surpassing diffraction limit. Strong coupling between a plasmonic nanocavity and molecule forms hybrid upper lower branch states, resulting Rabi splitting (RS) optical spectra. However, scattering absorption spectra often fail to unambiguously distinguish whether double peaks arise from energy transparency or RS. In contrast, photoluminescence (PL)...

10.1515/nanoph-2024-0580 article EN cc-by Nanophotonics 2025-02-15

We demonstrate the size-dependent separation and permanent immobilization of DNA on plasmonic substrates by means optical tweezers. found that a gold nanopyramidal dimer array enhanced force exerted DNA, leading to substrate. The was realized combination plasmon-enhanced thermophoretic induced photothermal effect plasmons. In this study, we applied phenomenon fixation size-different DNA. During plasmon excitation, strands different sizes became permanently immobilized substrate forming...

10.1038/s41598-020-60165-5 article EN cc-by Scientific Reports 2020-02-25

The five schemes are resistive-load-based deadbeat (DB) control, disturbance-observer-based DB control I. II, internal-model-principle-based pole placement, and digital proportional-integral (PI) control. applicable to single-phase three-phase balanced-load inverter systems because the balanced system can be converted two decoupled single phase systems. modification of law from a is explained. Simulations were performed in both systems, experiments carried out PWM system. I PI yielded best...

10.1109/ias.1990.152307 article EN Conference Record of the 1988 IEEE Industry Applications Society Annual Meeting 2002-12-04

We theoretically study the DC Josephson effect of a semiconductor nanowire (NW) with strong spin-orbit interaction when magnetic field is applied parallel to NW. adopt model single scatterer in quasi-one-dimensional system for case short junctions where size normal region much smaller than coherent length. In conduction channel model, we obtain analytical expressions energy levels Andreev bound states, $E_n$, and supercurrent $I$, as function phase difference $\varphi$ between two...

10.7566/jpsj.82.054703 article EN Journal of the Physical Society of Japan 2013-04-15

A new approach for real time digital feedback control of PWM inverter is proposed, in which an ideal instantaneous deadbeat realized without any sampling compensation method using FPGA based hardware controller. Deadbeat ensures the state variables matches at each instants every period. Generally this kind system on DSP software controller, so some technique necessary because kth instant cannot be used outputs In paper, a novel to realize dead-beat controller proposed. The enables almost its...

10.1109/iecon.2003.1279976 article EN 2004-05-25

A new power train for electric vehicles is proposed using an anti-directional twin rotary (ADTR) motor. stator in a conventional motor was reformed to be movable, and the (outer rotor) rotates opposite direction inner rotor. In this paper, several characteristics of induction motor-type ADTR are reported. When used vehicles, one rotors should reversed both rotate same direction, propelling two wheels vehicle. The torque can balanced without differential gear. fundamental torque-balancing...

10.1109/41.557500 article EN IEEE Transactions on Industrial Electronics 1997-01-01

We propose an efficient spin filter including antidot fabricated on semiconductor heterostructures with strong spin-orbit interaction. The creates a tunable potential two-dimensional electron gas in the heterostructures, which may be attractive as well repulsive. Our idea is based enhancement of extrinsic Hall effect by resonant scattering when properly tuned. Numerical studies for three- and four-terminal devices indicate that efficiency can more than 50% tuning to condition.

10.1103/physrevb.80.125311 article EN Physical Review B 2009-09-15

This paper proposes a new general Space Vector PWM (SVPWM) method for Multi-Level Inverters (MLI) based on generalization of dwell-times calculation. The presented scheme is developed Cascaded H-Bridge (CHB) inverter. In the proposed strategy, sectors are defined by two parameters serving easy calculation dwell-times. A very simple mapping used to achieve SVPWM any n-level addition dead-band hysteresis introduced in algorithm avoid output voltage level jumping. simulation results show...

10.1109/epepemc.2012.6397476 article EN 2012-09-01

We consider the spectrum of Andreev bound states (ABSs) in an exemplary four-terminal superconducting structure where four chaotic cavities are connected by quantum point contacts to terminals and each other forming a ring. nickname resulting device 4T-ring. Such tunable can be realized 2D electron gas-superconductor or graphene-based hybrid structure. concentrate on limit short large conductance there many ABS quasicontinuous spectrum. The energies tuned changing phases terminals. observe...

10.1103/physrevb.95.045411 article EN Physical review. B./Physical review. B 2017-01-12

The optical binding of many particles has the potential to achieve wide-area formation a "crystal" small materials. Unlike conventional binding, where entire assembly targeted is directly irradiated with light, if remote can be indirectly manipulated using single trapped particle through degrees freedom create ordered structures enhanced. In this study, we theoretically investigate dynamics gold nanoparticles that are by focused laser. We demonstrate rotational motion an indirect force and...

10.1364/oe.479643 article EN cc-by Optics Express 2023-01-04

The Josephson junction (JJ) is an essential element of superconducting (SC) devices for both fundamental and applied physics. short-range coherent coupling two adjacent JJs forms the Andreev molecule states (AMSs), which will provide a new ingredient to engineer SC transport in control qubits. However, no experimental evidence AMSs coupled has been reported. Here we tunnel spectroscopic results electrically controllable planar sharing one electrode. We discover that JJ are highly modulated...

10.48550/arxiv.2303.10540 preprint EN cc-by arXiv (Cornell University) 2023-01-01

In this paper, a new control method for the utility interactive inverter based on deadbeat with FPGA hardware controller is proposed. Deadbeat one to ensure output voltage or current matches references at sampling instant, so adopting inverter, response of system much improved small LC filter component compared conventional PI control, which results in improvement cost performance inverter. Also, utilize capability controller, multi proposed, enables 1 MHz while carrier period improve...

10.1109/epe.2005.219349 article EN European Conference on Power Electronics and Applications 2005-01-01

The Tokyo University Egogram (TEG) has been recognized as a valuable psychological tool for transactional analysis (TA). TEG revised from version 2 to 3, and the authors have investigated its use in research involving university students. key findings were follows: high prevalence of AC-dominant (dependent) types, occurrence CP-low (gentle) dominant child (C) types more common than parent (P) few cases A-dominant observed, regardless whether students science technology departments. rate...

10.36502/2024/hcr.6237 article EN 2024-10-21
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