Results for "Kenji Watanabe"
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Simulation of Transitions between "Pasta" Phases in Dense MatterAug 24 2004Jan 28 2005Calculations of equilibrium properties of dense matter predict that at subnuclear densities nuclei can be rodlike or slablike. To investigate whether transitions between phases with non-spherical nuclei can occur during the collapse of a star, we perform ... More Dry transfer of CVD graphene using MoS$_2$-based stampsJun 01 2017Recently, a contamination-free dry transfer method for graphene grown by chemical vapor deposition (CVD) has been reported that allows to directly pick-up graphene from the copper growth substrate using a flake of hexagonal boron nitride (hBN), resulting ... More Dry-transferred CVD graphene for inverted spin valve devicesSep 05 2017Integrating high-mobility graphene grown by chemical vapor deposition (CVD) into spin transport devices is one of the key tasks in graphene spintronics. We use a van der Waals pickup technique to transfer CVD graphene by hexagonal boron nitride (hBN) ... More BN/Graphene/BN Transistors for RF ApplicationsAug 09 2011In this letter, we demonstrate the first BN/Graphene/BN field effect transistor for RF applications. The BN/Graphene/BN structure can preserve the high mobility of graphene, even when it is sandwiched between a substrate and a gate dielectric. Field effect ... More Boundary Scattering in Ballistic GrapheneMay 23 2012We report magnetotransport measurements in ballistic graphene/hexagonal boron nitride mesoscopic wires where the charge carrier mean free path is comparable to wire width $W$. Magnetoresistance curves show characteristic peak structures where the peak ... More Ballistic transport exceeding 28 μm in CVD grown grapheneNov 27 2015Jan 12 2016We report on ballistic transport over more than 28 \mu m in graphene grown by chemical vapor deposition (CVD) that is fully encapsulated in hexagonal boron nitride. The structures are fabricated by an advanced dry van-der-Waals transfer method and exhibit ... More Loop series expansion with propagation diagramsAug 08 2008Nov 13 2008The Bethe approximation is a successful method for approximating partition functions of probabilistic models associated with a graph. Recently, Chertkov and Chernyak derived an interesting formula called Loop Series Expansion, which is an expansion of ... More High-quality dry transferred CVD bilayer grapheneApr 14 2017We report on the fabrication and characterization of high-quality chemical vapor-deposited (CVD) bilayer graphene (BLG). In particular, we demonstrate that CVD-grown BLG can mechanically be detached from the copper foil by an hexagonal boron nitride (hBN) ... More Angular Power Spectrum in Modular Invariant Inflation ModelSep 25 2006Nov 28 2006We propose a scalar potential of inflation, motivated by modular invariant supergravity, and compute the angular power spectra of the adiabatic density perturbations that result from this model. The potential consists of three scalar fields, S, Y and ... More Imaging Electron Motion in a Few Layer MoS2 DeviceAug 07 2016Ultrathin sheets of MoS2 are a newly discovered 2D semiconductor that holds great promise for nanoelectronics. Understanding the pattern of current flow will be crucial for developing devices. In this talk, we present images of current flow in MoS2 obtained ... More Exciton energy-momentum map of hexagonal boron nitrideAug 07 2015Understanding and controlling the way excitons propagate in solids is a key for tailoring materials with improved optoelectronic properties. A fundamental step in this direction is the determination of the exciton energy-momentum dispersion. Here, thanks ... More Photo-thermionic effect in vertical graphene heterostructuresJan 16 2016Jun 10 2016Finding alternative optoelectronic mechanisms that overcome the limitations of conventional semiconductor devices is paramount for detecting and harvesting low-energy photons. A highly promising approach is to drive a current from the thermal energy added ... More Evidence for a Spin Phase Transition at ν=0 in Bilayer GrapheneDec 16 2012Feb 16 2013The most celebrated property of the quantum spin Hall effect is the presence of spin-polarized counter-propagating edge states. This novel edge state configuration has also been predicted to occur in graphene when spin-split electron- and hole-like Landau ... More Nonlinear Transport of Graphene in the Quantum Hall RegimeNov 14 2016We have studied the breakdown of the integer quantum Hall (QH) effect with fully broken symmetry, in an ultra-high mobility graphene device sandwiched between two single crystal hexagonal boron nitride substrates. The evolution and stabilities of the ... More Order parameters with higher dimensionful composite fieldsDec 23 2003We discuss the possibility of the spontaneous symmetry breaking characterized by order parameters with higher dimensionful composite fields. By analyzing general Ginzburg-Landau potential for a complex scalar field \phi=\phi_1 + i \phi_2 with O(2) symmetry, ... More Inducing Superconducting Correlation in Quantum Hall Edge StatesSep 26 2016Sep 28 2016The quantum Hall (QH) effect supports a set of chiral edge states at the boundary of a 2-dimensional electron gas (2DEG) system. A superconductor (SC) contacting these states induces correlation of the quasi-particles in the dissipationless 1D chiral ... More Hot Carrier-Assisted Intrinsic Photoresponse in GrapheneAug 18 2011Nov 17 2011Graphene is a new material showing high promise in optoelectronics, photonics, and energy-harvesting applications. However, the underlying physical mechanism of optoelectronic response has not been established. Here, we report on the intrinsic optoelectronic ... More Spin and valley quantum Hall ferromagnetism in grapheneJan 19 2012In a graphene Landau level (LL), strong Coulomb interactions and the fourfold spin/valley degeneracy lead to an approximate SU(4) isospin symmetry. At partial filling, exchange interactions can spontaneously break this symmetry, manifesting as additional ... More Large N Expansion for Strongly-coupled Boson-Fermion MixturesOct 20 2010We study a many-body mixture of an equal number of bosons and two-component fermions with a strong contact attraction. In this system bosons and fermions can be paired into composite fermions. We construct a large N extension where both bosons and fermions ... More Asymptotic States in Two Black Hole Moduli SpaceJul 27 2004Oct 14 2004We discuss the quantum states in the moduli space, which constructed with maximally charged dilaton black holes. Considering the quantum mechanics in the moduli space, we obtain the asymptotic states for the near-coincident black holes and the widely ... More Floer homology of Lagrangian submanifoldsJun 24 2011This is a translation of an article appeared in Japanese in Suugaku 63 (2011), no. 1, 43-66 (MR2790665) and is a survey of Lagrangian Floer homology which the author studies jointly with Y.-G.Oh, H. Ohta, and K. Ono. It also contains some explanation ... More Exceptional String: Instanton Expansions and Seiberg-Witten CurveOct 15 2001Feb 25 2002We investigate instanton expansions of partition functions of several toric E-string models using local mirror symmetry and elliptic modular forms. We also develop a method to obtain the Seiberg--Witten curve of E-string with arbitrary Wilson lines with ... More Kähler Moduli Space of a D-Brane at Orbifold SingularitiesJun 08 1998Jun 10 1998We develop a method to analyze systematically the configuration space of a D-brane localized at the orbifold singular point of a Calabi--Yau $d$-fold of the form ${\Bbb C}^d/\Gamma$ using the theory of toric quotients. This approach elucidates the structure ... More D-Branes and Quotient Singularities of Calabi-Yau FourfoldsJul 01 1997Mar 02 1998We investigate a (0,2) gauge theory realized on the world volume of the type IIB D1-brane at the singular point of a Calabi-Yau fourfold. It is argued that the gauge anomaly can be canceled via coupling to the R-R chiral bosons in bulk IIB string. We ... More Bounded Optimal Exploration in MDPApr 05 2016Within the framework of probably approximately correct Markov decision processes (PAC-MDP), much theoretical work has focused on methods to attain near optimality after a relatively long period of learning and exploration. However, practical concerns ... More Rotation and multiple stellar population in globular clustersOct 19 2010We investigate structure and kinematics of the second generation of stars (SG) formed from gaseous ejecta of the first generation of stars (FG) in forming globular clusters (GCs). We consider that SG can be formed from gaseous ejecta from AGB stars of ... More Evolving Glasma and Kolmogorov SpectrumNov 04 2011Nov 13 2011We present a pedagogical introduction to the theoretical framework of the Color Glass Condensate (CGC) and the McLerran-Venugopalan (MV) model. We discuss the application of the MV model to describe the early-time dynamics of the relativistic heavy-ion ... More When was the Large Magellanic Cloud accreted onto the Galaxy ?Jun 13 2011Using fully self-consistent N-body models for the dynamical evolution of the Large Magellanic Cloud (LMC) in the Galaxy, we show that if the LMC initially has an extended old stellar halo before its commencement of tidal interaction with the Galaxy, physical ... 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