Quantum Optical Physics Research Group
Optical Science Laboratories
NTT Basic Research Laboratories
Nippon Telegraph and Telephon Corporation
E-mail:email address
2005-2012Department of Materials Science, Tohoku University
2012 Ph.D (Engineering), Tohoku University
2012- NTT Basic Research Laboratories

Recent works
  • Gate-controlled persistent spin helix state in (In,Ga)As quantum wells
    M. Kohda, V. Kechner, Y. Kunihashi, T. Dollinger, P. Olbrich, C. Schonhuber, I. Caspers, V. V. Bel'kov, L. E. Golub, D. Weiss, K. Richter, J. Nitta, and S. D. Ganichev
    Physical Review B 86, 081306(R) (2012).
    In layered semiconductors with spin-orbit interaction (SOI) a persistent spin helix (PSH) state with suppressed spin relaxation is expected if the strengths of the Rashba and Dresselhaus SOI terms, alpha and beta, are equal. Here we demonstrate gate control and detection of the PSH in two-dimensional electron systems with strong SOI including terms cubic in momentum.

  • Anisotropic Weak Anti-Localization under In-Plane Magnetic Field and Control of Dimensionality via Spin Precession Length
    S. Nonaka, Y. Kunihashi, M. Kohda, and J. Nitta
    Japanese Journal of Applied Physics 51, 04DM01 (2012).
    We have examined the newly proposed method in order to electrically deduce the ratio between the Rashba and Dresselhaus spin-orbit interaction (SOI) parameters. From the comparison between experiments and calculated Rashba SOI parameters, we have found that the method is applicable only when the wire width is shorter than the spin precession length.

  • Proposal of spin complementary field effect transistor
    Y. Kunihashi, M. Kohda, H. Sanada, H. Gotoh, T. Sogawa, and J. Nitta
    Applied Physics Letters 100, 113502 (2012).
    Spin complementary field effect transistor is proposed on the basis of gate-controlled persistent spin helix (PSH) states. Our proposed device could be a reconfigurable minimum unit of the spin-based logic circuit.

  • Semiclassical approach for spin dephasing in a quasi-one-dimensional channel
    Y. Kunihashi, M. Kohda, and J. Nitta
    Physical Review B 85, 035321 (2012).
    We derived the spin dephasing time taking Rashba and Dresselhaus spin- orbit interactions (SOI) into account in a quasi-one-dimensional (1D) system. We herein proposed quantitative estimation of the cubic Dresselhaus SOI as well as other SOIs by optical measurement of the crystal orientation dependence of spin dephasing time in quasi-1D wires.

  • Experimental Demonstration of Spin Geometric Phase: Radius Dependence of Time-Reversal Aharonov-Casher Oscillations
    F. Nagasawa, J. Takagi, Y. Kunihashi, M. Kohda, and J. Nitta
    Physical Review Letters 108, 086801 (2012).
    A geometric phase of electron spin is studied in arrays of InAlAs/InGaAs two-dimensional electron gas rings. We conclude that the shift is due to a modulation of the spin geometric phase, the maximum modulation of which is approximately 1.5 rad.

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