Kyushu University Academic Staff Educational and Research Activities Database
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Harada Yuichi Last modified date:2018.10.16

Graduate School
Other Organization

NanoFactory research platform at KOINE division .
Academic Degree
Ph. D.
Country of degree conferring institution (Overseas)
Field of Specialization
Condensed Matter Physics I, Superconducting device, Nanotechnology, and surface engineering
ORCID(Open Researcher and Contributor ID)
Total Priod of education and research career in the foreign country
Outline Activities
KOINE is the abbreviation of Kyudai global Open Innovation Network Engine, but is English word originated from ancient Greek. English work, koine represents common language. KOINE concept provides the opportunities to meet and discuss freely by people with different backgrounds and we expect such discussion can create multidisciplinary researches as well as new and innovative industrial applications. KOINE concept promotes various research platforms and we study what is the essence of innovative creation and how innovative idea comes out. Currently six KOINE platforms are working. Anyone who wants to create new research fields and industry and/or wants to solve complicated problems feel freely to contact us.
Research Interests
  • Industrial-academia research collaborations based on KOINE model or Kyudai global Open Innovation Network Engine that is an original open innovation system.
    keyword : Open Innovation
  • Study on the management of the collaborative research projects among industry, academia, and government
    Innovative education
    keyword : management of the collaborative research
Academic Activities
1. Hiroshi Irie, Clements Todt, Norio Kumada, Harada, Yuichi, Hiroki Sugiyama, Tatsushi Akazaki, Koji Muraki, Andreev reflection and bound state formation in a ballistic two-dimensional electron gas probed by a quantum point contact, Physical Review B, 10.1103/PhysRevB.94.155305, 94, 155305-6, 2016.10, We study coherent transport and bound state formation of Bogoliubov quasiparticles in a high-mobility In0.75Ga0.25As two-dimensional electron gas (2DEG) coupled to a superconducting Nb electrode by means of a quantum point contact (QPC) as a tunable single-mode probe. Below the superconducting critical temperature of Nb, the QPC shows a single-channel conductance greater than the conductance quantum 2e2/h at zero bias, which indicates the presence of Andreev-reflected quasiparticles, time-reversed states of the injected electron, returning back through the QPC. The marked sensitivity of the conductance enhancement to voltage bias and perpendicular magnetic field suggests a mechanism analogous to reflectionless tunneling—a hallmark of phase-coherent transport, with the boundary of the 2DEG cavity playing the role of scatterers. When the QPC transmission is reduced to the tunneling regime, the differential conductance vs bias voltage probes the single-particle density of states in the proximity area. Measured conductance spectra show a double peak within the superconducting gap of Nb, demonstrating the formation of Andreev bound states in the 2DEG. Both of these results, obtained in the open and closed geometries, underpin the coherent nature of quasiparticles, i.e., phase-coherent Andreev reflection at the InGaAs/Nb interface and coherent propagation in the ballistic 2DEG..
2. Harada, Yuichi, Iriel, Hiroshi, Sugiyama, Hiroki, Akazaki, Tatsushi, Josephson coupling through one-dimensional ballistic channel in semiconductor-superconductor hybrid quantum point contacts, PHYSICAL REVIEW B, 10.1103/PhysRevB.89.165415, 89, 16, 2014.04, We study a superconducting quantum point contact made of a narrow In0.75Ga0.25As channel with Nb proximity electrodes. The narrow channel is formed in a gate-fitted constriction of InGaAs/InAlAs/InP heterostructure hosting a two-dimensional electron gas.When the channel opening is varied with the gate, the Josephson critical current exhibits a discretized variation that arises from the quantization of the transverse momentum in the channel. The quantization of Josephson critical current persists down to the single-channel regime, providing an unambiguous demonstration of a semiconductor-superconductor hybrid Josephson junction involving only a single ballistic channel..
Membership in Academic Society
  • American Physical Society
  • Institute of Electrical and Electronics Engineers
  • The Institute of Electronics, Information and Communication Engineers
  • The Japan Society of Applied Physics
Educational Activities
Engagement of practical research management, and nanotechnology and nano science.