Two-dimensional system
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>>Quantum dots/Nanowire
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>>Low-temperature nanoprobe
Two-Dimensional System
We investigate many-body effects in two-dimensional systems, particularly in quantum Hall systems, formed in GaAs/AlGaAs or Si/SiO2 heterostructures and in graphene by transport or nuclear spin measurements.
Figure: Spin polarization in a high-mobility GaAs/AlGaAs QH system detected by NMR [Science 335, 828 (2012)].

Selected publications
  • GaAs/AlGaAs quantum Hall system
    • NMR probing of spin and charge order near odd-integer filling in the second Landau level
      T. D. Rhone, L. Tiemann, and K. Muraki
      Phys. Rev. B 92, 041301(R) (2015).

    • NMR profiling of quantum electron solids in high magnetic fields
      L. Tiemann, T. D. Rhone, N. Shibata, K. Muraki
      Nature Physics 10, 648 (2014).

    • Fractionalized wave packets from an artificial Tomonaga-Luttinger liquid
      H. Kamata, N. Kumada, M. Hashisaka, K. Muraki, and T. Fujisawa
      Nature Nanotech. 9, 177 (2014).

    • nu=5/2 fractional quantum Hall state in low-mobility electron systems: Different roles of disorder
      Gerardo Gamez and Koji Muraki
      Phys. Rev. B 88, 075308 (2013).

    • Unraveling the Spin Polarization of the nu = 5/2 Fractional Quantum Hall State
      L. Tiemann, G. Gamez, N. Kumada, and K. Muraki
      Science 335, 828 (2012).

    • Low-Frequency Spin Fluctuations in Skyrmions Confined by Wires: Measurements of Local Nuclear Spin Relaxation
      Takashi Kobayashi, Norio Kumada, Takeshi Ota, Satoshi Sasaki, and Yoshiro Hirayama
      Phys. Rev. Lett. 107, 126807 (2011).

    • Edge magnetoplasmon transport in gated and ungated quantum Hall systems
      N. Kumada, H. Kamata, and T. Fujisawa
      Phys. Rev. B 84, 045314 (2011).

    • Voltage-controlled group velocity of edge magnetoplasmon in the quantum Hall regime
      H. Kamata, T. Ota, K. Muraki, and T. Fujisawa
      Phys. Rev. B 81, 085329 (2010).

    • Intrinsic Gap and Exciton Condensation in the nu_T=1 Bilayer System
      P. Giudici, K. Muraki, N. Kumada, and T. Fujisawa
      Phys. Rev. Lett. 104, 056802 (2010).

    • Spin-dependent phase diagram of the nu_T=1 bilayer electron system
      P. Giudici, K. Muraki, N. Kumada, Y. Hirayama, and T. Fujisawa
      Phys. Rev. Lett. 100, 106803 (2008).

    • Modulation of bilayer quantum Hall states by tilted-field-induced subband-Landau-level coupling
      N. Kumada, K. Iwata, K. Tagashira, Y. Shimoda, K. Muraki, Y. Hirayama, and A. Sawada
      Phys. Rev. B. 77, 155324 (2008).

    • NMR Evidence for Spin Canting in a Bilayer nu = 2 Quantum Hall System
      N. Kumada, K. Muraki, and Y. Hirayama
      Phys. Rev. Lett. 99, 076805 (2007).

    • Low-Frequency Spin Dynamics in a Canted Antiferromagnet
      N. Kumada, K. Muraki, and Y. Hirayama
      Science 313, 329 (2006.)

    • Spin Degree of Freedom in the nu = 1 Bilayer Electron System Investigated by Nuclear Spin Relaxation
      N. Kumada, K. Muraki, K. Hashimoto, and Y. Hirayama
      Phys. Rev. Lett. 94, 096802 (2005).

    • Coulomb drag as a probe of the nature of compressible states in a magnetic field
      K. Muraki, J. G. S. Lok, S. Kraus, W. Dietsche, K. von Klitzing, D. Schuh, M. Bichler, and W. Wegscheider
      Phys. Rev. Lett. 92, 246801 (2004).

    • Phase diagram of interacting composite fermions in the bilayer nu=2/3 quantum Hall effect
      N. Kumada, D. Terasawa, Y. Shimoda, H. Azuhata, A. Sawada, Z. F. Ezawa, K. Muraki, T. Saku, and Y. Hirayama
      Phys. Rev. Lett. 89, 116802 (2002).

    • Charge excitations in easy-axis and easy-plane quantum Hall ferromagnets
      K. Muraki, T. Saku, and Y. Hirayama
      Phys. Rev. Lett. 87, 196801 (2001).

  • Graphene
    • Evaluation of disorder introduced by electrolyte gating through transport measurements in graphene
      Andrew Browning, Norio Kumada, Yoshiaki Sekine, Hiroshi Irie, Koji Muraki, and Hideki Yamamoto
      Appl. Phys. Express 9, 065102 (2016).

    • Probing the extended-state width of disorder-broadened Landau levels in epitaxial graphene
      K. Takase, H. Hibino, and K. Muraki
      Phys. Rev. B 92, 125407 (2015).

    • Shot noise generated by graphene p-n junctions in the quantum Hall effect regime
      N. Kumada, F. D. Parmentier, H. Hibino, D. C. Glattli, and P. Roulleau
      Nature Commun. 6, 8068 (2015).

    • Resonant Edge Magnetoplasmons and Their Decay in Graphene
      N. Kumada, P. Roulleau, B. Roche, M. Hashisaka, H. Hibino, I. Petkovic, and D. C. Glattli
      Phys. Rev. Lett. 113, 266601 (2014).

    • Plasmon transport and its guiding in graphene
      N. Kumada, R. Dubourget, K. Sasaki, S. Tanabe, H. Hibino, H. Kamata, M. Hashisaka, K. Muraki and T. Fujisawa
      New J. Phys. 16, 063055 (2014).

    • Plasmon transport in graphene investigated by time-resolved electrical measurements
      N. Kumada, S. Tanabe, H. Hibino, H. Kamata, M. Hashisaka, K. Muraki
      Nature Commun. 4, 1363 (2013).

    • Impact of graphene quantum capacitance on transport spectroscopy
      K. Takase, S. Tanabe, S. Sasaki, H. Hibino, and K. Muraki
      Phys. Rev. B 86, 165435 (2012).

  • Topological insulator
    • Single-edge transport in an InAs/GaSb quantum spin Hall insulator
      Francois Couedo, Hiroshi Irie, Kyoichi Suzuki, Koji Onomitsu, and Koji Muraki
      Phys. Rev. B 94, 035301 (2016).

    • Engineering quantum spin Hall insulators by strained-layer heterostructures
      T. Akiho, F. Couedo, H. Irie, K. Suzuki, K. Onomitsu, and K. Muraki
      Appl. Phys. Lett. 109, 192105 (2016).

    • Gate-controlled semimetal-topological insulator transition in an InAs/GaSb heterostructure
      Kyoichi Suzuki, Yuichi Harada, Koji Onomitsu, and Koji Muraki
      Phys. Rev. B 91, 245309 (2015).

    • Edge channel transport in the InAs/GaSb topological insulating phase
      Kyoichi Suzuki, Yuichi Harada, Koji Onomitsu, and Koji Muraki
      Phys. Rev. B 87, 235311 (2013).

    • Landau-level Hybridization and the Quantum Hall Effect in InAs/(AlSb)/GaSb Electron-Hole System
      K. Suzuki, K. Takashina, S. Miyashita, and Y. Hirayama
      Phys. Rev. Lett. 93, 016803 (2004).

  • Superconductor/semiconductor hybrid system
    • Andreev reflection and bound state formation in a ballistic two-dimensional electron gas probed by a quantum point contact
      Hiroshi Irie, Clemens Todt, Norio Kumada, Yuichi Harada, Hiroki Sugiyama, Tatsushi Akazaki, and Koji Muraki,
      Phys. Rev. B 94, 155305 (2016).

    • Josephson coupling through one-dimensional ballistic channel in semiconductor-superconductor hybrid quantum point contacts
      Hiroshi Irie, Yuichi Harada, Hiroki Sugiyama, and Tatsushi Akazaki
      Phy. Rev. B 89, 165415 (2014).

  • Electron-nuclear spin interactions
    • Electric Field Induced Nuclear Spin Resonance Mediated by Oscillating Electron Spin Domains in GaAs-Based Semiconductors
      N. Kumada, T. Kamada, S. Miyashita, Y. Hirayama, and T. Fujisawa
      Phys. Rev. Lett. 101, 137602 (2008).

    • Decoherence of nuclear spins due to dipole-dipole interactions probed by resistively detected nuclear magnetic resonance
      T. Ota, G. Yusa, N. Kumada, S. Miyashita, T. Fujisawa, and Y. Hirayama
      Appl. Phys. Lett. 91, 193101 (2007).

    • Nuclear spin population and its control toward initialization using an all-electrical submicron scale nuclear magnetic resonance device
      T. Ota, G. Yusa, N. Kumada, S. Miyashita, and Y. Hirayama
      Appl. Phys. Lett. 90, 102118 (2007).

    • Controlled multiple quantum coherences of nuclear spins in a nanometre-scale device
      G. Yusa, K. Muraki, K. Takashina, K. Hashimoto, and Y. Hirayama
      Nature 434, 1001 (2005).

    • Effects of inversion asymmetry on electron-nuclear spin coupling in semiconductor heterostructures: Possible role of spin-orbit interactions
      K. Hashimoto, K. Muraki, N. Kumada, T. Saku, and Y. Hirayama
      Phys. Rev. Lett. 94, 146601 (2005).

    • Electrically controlled nuclear spin polarization and relaxation by quantum-Hall states
      K. Hashimoto, K. Muraki, T. Saku, and Y. Hirayama
      Phys. Rev. Lett. 88, 176601 (2002).

  • Si/SiO2 heterostructures
    • Impact of Valley Polarization on the Resistivity in Two Dimensions
      K. Takashina, Y. Niida, V. T. Renard, A. Fujiwara, T. Fujisawa, K. Muraki, and Y. Hirayama
      Phys. Rev. Lett. 106, 196403 (2011).

    • Electrons and holes in a 40 nm thick silicon slab at cryogenic temperatures
      K. Takashina, K. Nishiguchi, Y. Ono, A. Fujiwara, T. Fujisawa, Y. Hirayama, and K. Muraki
      Appl. Phys. Lett. 94, 142104 (2009).

    • Spin splitting of upper electron subbands in a SiO2/Si(100)/SiO2 quantum well with in-plane magnetic field
      Y. Niida, K. Takashina, A. Fujiwara, T. Fujisawa, and Y. Hirayama
      Appl. Phys. Lett. 94, 142101 (2009).

    • Anomalous Resistance Ridges along Filling Factor nu=4i
      K. Takashina, M. Brun, T. Ota, D. K. Maude, A. Fujiwara, Y. Ono, Y. Takahashi, and Y. Hirayama
      Phys. Rev. Lett. 99, 036803 (2007).

    • Valley polarization in Si(100) at zero magnetic field
      K. Takashina, Y. Ono, A. Fujiwara, Y. Takahashi, and Y. Hirayama
      Phys. Rev. Lett. 96, 236801 (2006).

    • Valley splitting control in SiO2/Si/SiO2 quantum wells in the quantum Hall regime
      K. Takashina, A. Fujiwara, S. Horiguchi, Y. Takahashi, and Y. Hirayama
      Phys. Rev. B 69, 161304(R) (2004).

  • Other topics
    • Boundary-Mediated Electron-Electron Interactions in Quantum Point Contacts
      V. T. Renard, O. A. Tkachenko, V. A. Tkachenko, T. Ota, N. Kumada, J.-C. Portal, and Y. Hirayama
      Phys. Rev. Lett. 100, 186801 (2008).

3-1 Morinosato-Wakamiya, Atugi, Kanagawa 243-0198, Japan
Qauntum Solid State Physics Research Group
Physical Science Labortory
NTT Basic Research Laboratories
NTT