Results for "J. K. Ahn"

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RENO: An Experiment for Neutrino Oscillation Parameter theta_13 Using Reactor Neutrinos at YonggwangMar 06 2010The RENO experiment is a short baseline neutrino experiment in Korea aiming to measure the neutrino mixing angle theta_13 or set limit to sin^2(2 theta_13) less than 0.02. This document describes physics goals, experimental site, detector design, scintillator, ... More
New limit on the $K^0_L \to π^0 ν\barν$ decay rateJul 12 2006Sep 18 2006The first dedicated experiment for the rare kaon decay $K^0_L \to \pi^0 \nu \bar{\nu}$ has been performed by the E391a collaboration at the KEK 12-GeV proton synchrotron. A new upper limit of $2.1 \times 10^{-7}$ at the 90% confidence level was set for ... More
Anisotropy and temperature dependence of the optical conductivity in LaMnO_3Jan 14 1999May 04 1999A tight binding parameterization of the band structure, along with a mean field treatment of Hund, electron-electron, and electron-lattice couplings, is used to obtain the full optical conductivity tensor of LaMnO_3 as a function of temperature. We predict ... More
Symmetry-breaking skyrmion states in fractional quantum Hall systemsAug 15 1996Feb 05 1997We calculate in an analyical fashion the energies and net spins of skyrmions in fractional quantum Hall systems, based on the suggestion that skyrmion states are spontaneously $L_Z$ and $S_Z$ symmetry-breaking states. The quasihole-skyrmion state with ... More
Interplay of charge and orbital ordering in manganese perovskitesFeb 17 1998May 09 1998A model of localized classical electrons coupled to lattice degrees of freedom and, via the Coulomb interaction, to each other, has been studied to gain insight into the charge and orbital ordering observed in lightly doped manganese perovskites. Expressions ... More
Effects of uniaxial strain in LaMnO_3Apr 18 2000The effects of uniaxial strain on the structural, orbital, optical, and magnetic properties of LaMnO_3 are calculated using a general elastic energy expression, along with a tight-binding parameterization of the band theory. Tensile uniaxial strain of ... More
Search for the Decay $K^0_L \to π^0 ν\barν$Dec 27 2007Apr 27 2008We performed a search for the $K^0_L \to \pi^0 \nu \bar{\nu}$ decay at the KEK 12-GeV proton synchrotron. No candidate events were observed. An upper limit on the branching ratio for the decay was set to be $6.7 \times 10^{-8}$ at the 90% confidence level. ... More
Pairing in the quantum Hall systemOct 14 1997We find an analogy between the single skyrmion state in the quantum Hall system and the BCS superconducting state and address that the quantum mechanical origin of the skyrmion is electronic pairing. The skyrmion phase is found to be unstable for magnetic ... More
A microscopic theory of skyrmion excitations in the fractional quantum Hall systemAug 13 1996We present a microscopic theory of skyrmion and antiskyrmion excitations in fractional quantum Hall systems, and calculate in an analytical fashion their excitation energies. From the calculated net spins at various fractional filling factors, we find ... More
Heat Capacity of MgB_2: Evidence for Moderately Strong Coupling BehaviorFeb 23 2001Apr 17 2001We characterize the superconducting state of phase pure polycrystalline samples of the new layered superconductor MgB$_2$ by specific heat measurements in magnetic fields up to 9 T. The characteristic jump at the superconducting transition is observed ... More
Strain selection of charge and orbital ordering patterns in half-doped manganitesMay 19 2003Theoretical and computational results are presented clarifying the role of long-ranged strain interactions in determining the charge and orbital ordering in colossal magnetoresistance manganites. The strain energy contribution is found to be of order ... More
Correlation effects in a quantum dot at high magnetic fieldsOct 01 1995We investigate the effects of electron correlations on the ground state energy and the chemical potential of a droplet confined by a parabolic potential at high magnetic fields. We demonstrate the importance of correlations in estimating the transition ... More
Time-convolutionless reduced-density-operator theory of a noisy quantum channel: a two-bit quantum gate for quantum information processingJul 23 1999An exact reduced-density-operator for the output quantum states in time-convolutionless form was derived by solving the quantum Liouville equation which governs the dynamics of a noisy quantum channel by using a projection operator method and both advanced ... More
Experimental study of the decay $K_L^0\toπ^0ν\barν$Nov 25 2009Mar 26 2010The first dedicated search for the rare neutral-kaon decay $K_L^0\to\pi^0\nu\bar{\nu}$ has been carried out in the E391a experiment at the KEK 12-GeV proton synchrotron. The final upper limit of 2.6 $\times 10^{-8}$ at the 90% confidence level was set ... More
Dynamics and Spectral Weights of Shake-up Valence Excitations in Transition Metal K-edge Resonant Inelastic X-ray ScatteringDec 22 2004Aug 07 2008Using a model Hamiltonian, we discuss how we could interpret data obtained from transition metal $K$-edge resonant inelastic x-ray scattering (RIXS) experiments. By analyzing the creation of valence excitations from the screening of the core hole and ... More
Complete Nondiagonal Reflection Matrices of RSOS/SOS and Hard Hexagon ModelsOct 26 1997In this paper we compute the most general nondiagonal reflection matrices of the RSOS/SOS models and hard hexagon model using the boundary Yang-Baxter equations. We find new one-parameter family of reflection matrices for the RSOS model in addition to ... More
Spin fluctuations in the quasi-two dimensional Heisenberg ferromagnet GdI_2 studied by Electron Spin ResonanceJan 22 2004The spin dynamics of GdI_2 have been investigated by ESR spectroscopy. The temperature dependences of the resonance field and ESR intensity are well described by the model for the spin susceptibility proposed by Eremin et al. [Phys. Rev. B 64, 064425 ... More
Unusual Resistance Hysteresis in n-Layer Graphene Field Effect Transistors Fabricated on Ferroelectric Pb(Zr_0.2Ti_0.8)O_3Jul 07 2010We have fabricated n-layer graphene field effect transistors on epitaxial ferroelectric Pb(Zr_0.2Ti_0.8)O_3 (PZT) thin films. At low gate voltages, PZT behaves as a high-k dielectric with k up to 100. An unusual resistance hysteresis occurs in gate sweeps ... More
Comment on "Relevance of Cooperative Lattice Effects and Stress Fields in Phase-Separation Theories for CMR Manganites"Aug 03 2004We comment on a recent work by Burgy, Moreo, and Dagotto, Phys. Rev. Lett. V.92, 097202 (2004) (cond-mat/0308456).
Spontaneous Breaking of Parity in 2+1-Dimensional Thirring ModelApr 29 1994A new aspect of the vacuum structure of 2+1-dimensional Thirring model is presented. Using the Fierz identity, we split the current-current four-Fermi interaction in terms of a matrix valued auxiliary scalar field and compute its effective potential. ... More
Momentum dependence in K-edge resonant inelastic x-ray scattering and its application to screening dynamics in CE-phase La$_{0.5}$Sr$_{1.5}$MnO$_4$Aug 05 2013We present a formula for the calculation of K-edge resonant inelastic x-ray scattering on transition metal compounds, based on a local interaction between the valence shell electrons and the $1s$ core hole. Extending a previous result, we include explicit ... More
Reentrant Melting of Soliton Lattice Phase in Bilayer Quantum Hall SystemMar 25 2002Mar 26 2002At large parallel magnetic field $B_\parallel$, the ground state of bilayer quantum Hall system forms uniform soliton lattice phase. The soliton lattice will melt due to the proliferation of unbound dislocations at certain finite temperature leading to ... More
Response of Granulation to Small Scale Bright Features in the Quiet SunFeb 16 2011We detected 2.8 bright points (BPs) per Mm$^2$ in the Quiet Sun (QS) with the New Solar Telescope (NST) at Big Bear Solar Observatory; using the TiO 705.68 nm spectral line, at an angular resolution ~ 0.1'' to obtain 30 min data sequence. Some BPs formed ... More
Oscillatory behavior in the quiet Sun observed with the New Solar TelescopeJul 01 2010Surface photometry of the quiet Sun has achieved an angular resolution of $0".1$ with the New Solar Telescope at Big Bear Solar Observatory revealing that a disproportionate fraction of the oscillatory events appear above observed bright point-like structures. ... More
Nonlinear Dynamical Behaviors of the Equilibrium Longitudinal Distribution by Localized Wakes in an Electron Storage RingDec 04 2004We investigate the effects of a localized constant wake and a localized linear wake on the longitudinal beam distribution in equilibrium. We also examine the effects of the composite wake on the particle distribution when the constant wake and linear ... More
Integrating Functional Oxides with GrapheneApr 23 2012Graphene-oxide hybrid structures offer the opportunity to combine the versatile functionalities of oxides with the excellent electronic transport in graphene. Understanding and controlling how the dielectric environment affects the intrinsic properties ... More
Origin of the Non-Linear Pressure Effects in Perovskite Manganites: Buckling of Mn-O-Mn Bonds and Jahn-Teller Distortion of the MnO6 Octahedra Induced by PressureAug 14 2007Mar 21 2008High-pressure resistivity and x-ray diffraction have been measured on La0.85MnO3-d. At low pressures the metal-insulator transition temperature (TMI) increases linearly with pressure up to a critical pressure, P* ~ 3.4 GPa, which is followed by reduction ... More
Ground state properties of ferromagnetic metal/conjugated polymer interfacesSep 05 2002We theoretically investigate the ground state properties of ferromagnetic metal/conjugated polymer interfaces. The work is partially motivated by recent experiments in which injection of spin polarized electrons from ferromagnetic contacts into thin films ... More
High-Mobility Few-Layer Graphene Field Effect Transistors Fabricated on Epitaxial Ferroelectric Gate Oxides (Supplementary Information)Oct 29 2008Supplementary Information to arXiv:0810.4466: 1. Characterizations of Pb(Zr_0.2Ti_0.8)O_3 (PZT) films. 2. Substrate preparation before the exfoliation of graphene. 3. The band structure of FLG. 4. Dielectric constant measurements of PZT. 5. rho(V_g) and ... More
Epitaxial Growth of Multiferroic YMnO3 on GaNAug 19 2005In this work, we report on the epitaxial growth of multiferroic YMnO3 on GaN. Both materials are hexagonal with a nominal lattice mismatch of 4%, yet x-ray diffraction reveals an unexpected 30 degree rotation between the unit cells of YMnO3 and GaN that ... More
High-Mobility Few-Layer Graphene Field Effect Transistors Fabricated on Epitaxial Ferroelectric Gate OxidesOct 24 2008The carrier mobility \mu of few-layer graphene (FLG) field-effect transistors increases ten-fold when the SiO_2 substrate is replaced by single-crystal epitaxial Pb(Zr_0.2Ti_0.8)O_3 (PZT). In the electron-only regime of the FLG, \mu reaches 7x10^4 cm^2/Vs ... More
Measurement of Neutrino Oscillation by the K2K ExperimentJun 15 2006Dec 25 2006We present measurements of nu_mu disappearance in K2K, the KEK to Kamioka long-baseline neutrino oscillation experiment. One hundred and twelve beam-originated neutrino events are observed in the fiducial volume of Super-Kamiokande with an expectation ... More
Klein tunneling through an oblique barrier in graphene ribbonsJun 16 2010We study a transmission coefficient of graphene nanoribbons with a top gate which acts as an oblique barrier. Using a Green function method based on the Dirac-like equation, scattering among transverse modes due to the oblique barrier is taken into account ... More
Indications of Neutrino Oscillation in a 250 km Long-baseline ExperimentDec 04 2002Dec 16 2002The K2K experiment observes indications of neutrino oscillation: a reduction of $\nu_\mu$ flux together with a distortion of the energy spectrum. Fifty-six beam neutrino events are observed in Super-Kamiokande (SK), 250 km from the neutrino production ... More
Ultrafast quasiparticle relaxation dynamics in normal metals and heavy fermion materialsAug 11 2003Feb 18 2004We present a detailed theoretical study of the ultrafast quasiparticle relaxation dynamics observed in normal metals and heavy fermion materials with femtosecond time-resolved optical pump-probe spectroscopy. For normal metals, a nonthermal electron distribution ... More
Search for Electron Neutrino Appearance in a 250 km Long-baseline ExperimentFeb 10 2004Jun 14 2004We present a search for electron neutrino appearance from accelerator produced muon neutrinos in the K2K long baseline neutrino experiment. One candidate event is found in the data corresponding to an exposure of 4.8*10^19 protons on target. The expected ... More
Evaluation of Half-metallic Antiferromagnetism in ${\cal A}_2$CrFeO$_6$ ({$\cal A$}=La, SrApr 14 2012Jun 05 2012The nearly well-ordered double perovskite La$_2$CrFeO$_6$ has been synthesized recently. Contrary to previous theoretical predictions, but in agreement with experimental observations, our first principle calculations indicate an insulating ferrimagnet ... More
Electric Field Tuned Dimensional Crossover in Ar-Irradiated SrTiO3Sep 15 2009We present low temperature magnetoresistance measurements of Ar-irradiated SrTiO3 under an applied electrostatic field. The electric field, applied through a back gate bias, modulates both the mobility and sheet density, with a greater effect on the former. ... More
Optical Investigations of Charge Gap in Orbital Ordered La1/2Sr3/2MnO4Mar 22 1999Temperature and polarization dependent electronic structure of La1/2Sr3/2MnO4 were investigated by optical conductivity analyses. With decreasing temperature, for E//ab, a broad mid-infrared (MIR) peak of La1/2Sr3/2MnO4 becomes narrower and moves to the ... More
Photonic quantum ring laserNov 28 1998Dec 20 1998We report a quantum ring-like toroidal cavity naturally formed in a vertical-cavity-like active microdisk plane due to Rayleigh's band of whispering gallery modes. The $\sqrt{T}$-dependent redshift and a square-law property of microampere-range threshold ... More
Dynamic Spin Injection into Chemical Vapor Deposited GrapheneNov 02 2012We demonstrate dynamic spin injection into chemical vapor deposition (CVD) grown graphene by spin pumping from permalloy (Py) layers. Ferromagnetic resonance measurements at room temperature reveal a strong enhancement of the Gilbert damping at the Py/graphene ... More
Chromospheric signatures of small-scale flux emergence as observed with NST and Hinode instrumentsFeb 04 2011With the ever increasing influx of high resolution images of the solar surface obtained at a multitude of wavelengths, various processes occurring at small spatial scales have become a greater focus of our attention. Complex small-scale magnetic fields ... More
Specific heat of MgB$_2$ in a one- and a two-band model from first-principles calculationsNov 14 2001Jan 31 2002The heat capacity anomaly at the transition to superconductivity of the layered superconductor MgB$_2$ is compared to first-principles calculations with the Coulomb repulsion, $\mu^\ast$, as the only parameter which is fixed to give the measured $T_c$. ... More
Hole emitter whispering galleries of photonic quantum ringApr 18 2005We report on the first observation of hole whispering gallery lasers from semiconductor microcavities with three dimensional optical confinement, with thresholds potentially reducible to micro-to-nano ampere regimes according to a quadratic size-dependent ... More
Winding number and optical conductivity of multi-Weyl semimetalsSep 27 2016Multi-Weyl semimetals are a new type of Weyl semimetals which have anisotropic non-linear energy dispersion and a topological charge larger than one, thus exhibiting a unique quantum response. Using a unified lattice model we calculate the optical conductivity ... More
Resonant Coherent Phonon Generation in Single-Walled Carbon Nanotubes through Near-Band-Edge ExcitationDec 08 2009We have observed large-amplitude coherent phonon oscillations of radial breathing modes (RBMs) in single-walled carbon nanotubes excited through the lowest-energy (E11) interband transitions. In contrast to the previously-studied coherent phonons excited ... More
Test of CsI(Tl) crystals for the Dark Matter SearchOct 28 1999Searches for weakly interacting massive particles(WIMP) can be based on the dete ction of nuclear recoil energy in CsI(Tl) crystals. We demonstrate that low energy gamma rays down to few keV is detected with CsI(Tl) crystal detector. A clear peak at 6 ... More
Optical Investigations of La_{7/8}Sr_{1/8}MnO_3Sep 07 1998We investigated temperature dependent optical conductivity spectra of La_{7/8}Sr_{1/8}MnO_3. Its phonon bending mode starts to be splitted near a structural phase transition temperature. With further cooling, strength of a mid-infrared small polaron peak, ... More
Strong electron-phonon coupling in the rare-earth carbide superconductor La2C3Mar 11 2007We present the results of a crystal structure determination using neutron powder diffraction as well as the superconducting properties of the rare-earth sesquicarbide La2C3 (Tc ~ 13.4 K) by means of specific heat and upper critical field measurements. ... More
Quasiparticle relaxation dynamics in heavy fermion compoundsMay 26 2003We present the first femtosecond studies of electron-phonon (e-ph) thermalization in heavy fermion compounds. The e-ph thermalization time tau_{ep} increases below the Kondo temperature by more than two orders of magnitude as T = 0 K is approached. Analysis ... More
Detection of Accelerator-Produced Neutrinos at a Distance of 250 kmMar 01 2001The KEK to Kamioka long-baseline neutrino experiment (K2K) has begun its investigation of neutrino oscillations suggested by atmospheric neutrino observations. Twenty-eight neutrino events have been detected in coincidence with the expected arrival time ... More
Measurements and ab initio Molecular Dynamics Simulations of the High Temperature Ferroelectric Transition in Hexagonal RMnO3Oct 08 2011Measurements of the structure of hexagonal RMnO3 (R=rare earths (Ho) and Y) for temperatures significantly above the ferroelectric transition temperature (TFE) were conducted to determine the nature of the transition. The local and long range structural ... More
Electrodynamics of Nd0.7Sr0.3MnO3 Single Crystal investigated by Optical Conductivity AnalysesApr 13 1999We investigated temperature dependent optical conductivity spectra of Nd0.7Sr0.3MnO3 single crystal. We found that polishing and surface scattering effects on the Nd0.7Sr0.3MnO3 crystal surfaces could significantly distort the optical responses, especially ... More
Optical Conductivity of Manganites: Crossover from Jahn-Teller Small Polaron to Coherent Transport in the Ferromagnetic StateMar 16 1998We report on the optical properties of the hole-doped manganites Nd_{0.7}Sr _{0.3}MnO_{3}, La_{0.7}Ca_{0.3}MnO_{3}, and La_{0.7}Sr_{0.3}MnO_{3}. The low-energy optical conductivity in the paramagnetic-insulating state of these materials is characterized ... More
The charge ordered state in half-doped Bi-based manganites studied by $^{17}$O and $^{209}$Bi NMRMar 19 2005Apr 26 2005We present a $^{209}$Bi and $^{17}$O NMR study of the Mn electron spin correlations developed in the charge ordered state of Bi$_{0.5}$Sr$_{0.5}$MnO$_{3}$ and Bi$_{0.5}$Ca$_{0.5}$MnO$_{3}$. The unusually large local magnetic field $^{209}H_{loc}$ indicates ... More
Formation and Rupture of the Nanosized Metal Filament inside Oxide MatrixFeb 18 2011The paper presents a model of the electrically actuated formation and rupture of the nanosized metal filament inside oxide matrix. NiO oxide is used as an example for this model of ReRAM operation.
Resonant phonon coupling across the La{1-x}Sr{x}MnO{3}/SrTiO{3} interfaceFeb 20 2011Feb 28 2011The transport and magnetic properties of correlated La{0.53}Sr{0.47}MnO{3} ultrathin films, grown epitaxially on SrTiO{3}, show a sharp cusp at the structural transition temperature of the substrate. Using a combination of experiment and theory we show ... More
Spin-orbit interaction driven collective electron-hole excitations in a noncentrosymmetric nodal loop Weyl semimetalJul 13 2015Sep 23 2016NbP is one member of a new class of nodal loop semimetals characterized by the cooperative effects of spin-orbit coupling (SOC) and a lack of inversion center. Here transport and spectroscopic properties of NbP are evaluated using density functional theory ... More
Nematic domains and resistivity in an itinerant metamagnet coupled to a latticeApr 18 2006Mar 27 2007The nature of the emergent phase near a putative quantum critical point in the bilayer ruthenate Sr$_3$Ru$_2$O$_7$ has been a recent subject of intensive research. It has been suggested that this phase may possess electronic nematic order(ENO). In this ... More
Strongly momentum-dependent screening dynamics in La$_{0.5}$Sr$_{1.5}$MnO$_4$ observed with resonant inelastic x-ray scatteringOct 24 2012We report strongly momentum-dependent local charge screening dynamics in CE-type charge, orbital, and spin ordered La$_{0.5}$Sr$_{1.5}$MnO$_4$, based on Mn K-edge resonant inelastic x-ray scattering data. Through a comparison with theoretical calculations, ... More
Symmetry-mode-based classical and quantum mechanical formalism of lattice dynamicsJul 13 2007Aug 11 2012We present classical and quantum mechanical descriptions of lattice dynamics, from the atomic to the continuum scale, using atomic scale symmetry modes and their constraint equations. This approach is demonstrated for a one-dimensional chain and a two-dimensional ... More
Electronic properties of structural twin and antiphase boundaries in materials with strong electron-lattice couplingsSep 12 2003Aug 12 2004Using a symmetry-based atomic scale theory of lattice distortions, we demonstrate that elastic textures, such as twin and antiphase boundaries, can generate intricate electronic inhomogeneities in materials with strong electron-lattice coupling, as observed ... More
Core-Periphery Segregation in Evolving Prisoner's Dilemma NetworksMay 03 2011Dec 09 2012Dense cooperative networks are an essential element of social capital for a prosperous society. These networks enable individuals to overcome collective action dilemmas by enhancing trust. In many biological and social settings, network structures evolve ... More
Evidence for shape coexistence in $^{98}$MoOct 23 2013A $\gamma\gamma$ angular correlation experiment has been performed to investigate the low-energy states of the nucleus $^{98}$Mo. The new data, including spin assignments, multipole mixing ratios and lifetimes reveal evidence for shape coexistence and ... More
Measurement Limits to 134Cs Concentration in SoilJan 10 2009Dec 22 2011We investigate the caesium concentrations in soils in mountain areas near Gori nuclear power plant in Korea, focusing on the measurement limits to the 134Cs. In order to lower the minimum detectable amount (MDA) of activity for the 134Cs, we have used ... More
Atomic scale lattice distortions and domain wall profilesJul 09 2002Sep 02 2003We present an atomic scale theory of lattice distortions using strain related variables and their constraint equations. Our approach connects constrained {\it atomic length} scale variations to {\it continuum} elasticity and describes elasticity at several ... More
Small Scale Field Emergence and Its Impact on Photospheric GranulationJul 26 2012We used photospheric intensity images and magnetic field measurements from the New Solar Telescope in Big Bear and Helioseismic Magnetic Imager on board Solar Dynamics Observatory (SDO) to study the the effect that the new small-scale emerging flux induces ... More
Coupling between magnon and ligand-field excitations in magnetoelectric Tb3Fe5O12 garnetMay 15 2010The spectra of far-infrared transmission in Tb3Fe5O12 magnetoelectric single crystals have been studied in the range between 15 and 100 cm-1, in magnetic fields up to 10 T, and for temperatures between 5 and 150 K. We attribute some of the observed infrared-active ... More
Quantum error correction for continuously detected errorsFeb 01 2003Jul 24 2003We show that quantum feedback control can be used as a quantum error correction process for errors induced by weak continuous measurement. In particular, when the error model is restricted to one, perfectly measured, error channel per physical qubit, ... More
Continuous quantum error correction via quantum feedback controlOct 18 2001Oct 25 2001We describe a protocol for continuously protecting unknown quantum states from decoherence that incorporates design principles from both quantum error correction and quantum feedback control. Our protocol uses continuous measurements and Hamiltonian operations, ... More
MgB_2 under pressure: phonon calculations, Raman spectroscopy, and optical reflectanceMay 21 2001The effect of pressure on optical phonon frequencies of MgB$_2$ has been calculated using the frozen-phonon approach based on a pseudopotential method. Gr\"uneisen parameters of the harmonic mode frequencies are reported for the high-frequency zone-center ... More
Quantum phase retrieval of a Rydberg wave packet using a half-cycle pulseSep 15 2000Dec 11 2000A terahertz half-cycle pulse was used to retrieve information stored as quantum phase in an $N$-state Rydberg atom data register. The register was prepared as a wave packet with one state phase-reversed from the others (the "marked bit"). A half-cycle ... More
Transport through a Strongly Correlated Quantum-Dot with Fano InterferenceMar 16 2005We present the transport properties of a strongly correlated quantum dot attached to two leads with a side coupled non-interacting quantum dot. Transport properties are analyzed using the slave boson mean field theory which is reliable in the zero temperature ... More
A practical scheme for error control using feedbackFeb 03 2004May 20 2004We describe a scheme for quantum error correction that employs feedback and weak measurement rather than the standard tools of projective measurement and fast controlled unitary gates. The advantage of this scheme over previous protocols (for example ... More
Entanglement induced by a single-mode heat environmentSep 12 2001A thermal field, which frequently appears in problems of decoherence, provides us with minimal information about the field. We study the interaction of the thermal field and a quantum system composed of two qubits and find that such a chaotic field with ... More
Optically Driven Qubits in Artificial MoleculesMay 16 2000May 17 2000We present novel models of quantum gates based on coupled quantum dots in which a qubit is regarded as the superposition of ground states in each dot. Coherent control on the qubit is performed by both a frequency and a polarization of a monochromatic ... More
Relativity of EntanglementNov 02 2000Jan 18 2003It has recently been suggested that various entanglement measures for bipartite mixed states do not in general give the same ordering even in the asymptotic cases [S. Virmani and M. B. Plenio, Phys. Lett. A {\bf 268}, 31 (2000)]. That is, for two certain ... More
The magnetoresistance tensor of La(0.8)Sr(0.2)MnO(3)Oct 26 2008We measure the temperature dependence of the anisotropic magnetoresistance (AMR) and the planar Hall effect (PHE) in c-axis oriented epitaxial thin films of La(0.8)Sr(0.2)MnO(3), for different current directions relative to the crystal axes, and show ... More
Scanning SQUID Susceptometry of a paramagnetic superconductorApr 16 2012Scanning SQUID susceptometry images the local magnetization and susceptibility of a sample. By accurately modeling the SQUID signal we can determine the physical properties such as the penetration depth and permeability of superconducting samples. We ... More
Structural properties of the sesquicarbide superconductor La2C3 at high pressureMar 24 2005The effect of pressure on the structural properties of lanthanum sesquicarbide La2C3 (T_c = 13 K) has been investigated at room temperature by angle-dispersive powder x-ray diffraction in a diamond anvil cell. The compound remains in the cubic Pu2C3-type ... More
Effects of Hawking radiation and Wigner rotation on fermion entanglementApr 11 2006Sep 27 2006In this work, we report that the Hawking radiation effect on fermions is fundamentally different from the case of scalar particles. Intrinsic properties of fermions (exclusion principle and spin) affect strongly the interaction of fermions with both Hawking ... More
Inter-valley interactions in Si quantum dotsMay 08 2004Aug 16 2006In this paper, we studied the inter-valley interactions between the orbital functions associated with multi-valley of silicon (Si) quantum dots. Numerical calculations show that the inter-valley coupling between orbital functions increases rapidly with ... More
Holographic Supergravity Dual to Three Dimensional N=2 Gauge TheoryJun 09 2008Aug 08 2008By examining the previously known holographic N=2 supersymmetric renormalization group flow solution in four dimensions, we describe the mass-deformed Bagger-Lambert theory, that has SU(3)_I x U(1)_R symmetry, by the addition of mass term for one of the ... More
Two Circular Wilson Loops and Marginal DeformationsJun 08 2006Sep 06 2006We study type IIB supergravity backgrounds which are dual to marginal deformations of N=4 super Yang-Mills theory. We re-examine two circular Wilson loops and describe how the phase transition occurs in the presence of deformation parameter.
The Coset Spin-4 Casimir Operator and Its Three-Point Functions with ScalarsNov 01 2011Jan 23 2012We find the GKO coset construction of the dimension 4 Casimir operator that contains the quartic WZW currents contracted with completely symmetric SU(N) invariant tensors of ranks 4, 3, and 2. The requirements, that the operator product expansion with ... More
The Large N 't Hooft Limit of Coset Minimal ModelsJun 02 2011Oct 13 2011Recently, Gaberdiel and Gopakumar proposed that the two-dimensional WA_{N-1} minimal model conformal field theory in the large N 't Hooft limit is dual to the higher spin theories on the three-dimensional AdS space with two complex scalars. In this paper, ... More
New N=2 Supersymmetric Membrane Flow In Eleven-Dimensional SupergravitySep 21 2009Oct 21 2009We construct the 11-dimensional lift of the known N=2 supersymmetric RG flow solution in 4-dimensional N=8 gauged supergravity. The squashed and stretched 7-dimensional internal metric preserving SU(2) x U(1) x U(1)_R symmetry contains an Einstein-Kahler ... More
Meta-Stable Brane Configurations by Dualizing the Two Gauge GroupsApr 01 2008Oct 26 2009We consider the N=1 supersymmetric gauge theories with product gauge groups. The two kinds of D6-branes in the electric theory are both displaced and rotated respectively where these deformations are interpreted as the mass terms and quartic terms for ... More
Meta-Stable Brane Configurations, Multiple NS5-Branes, and Rotated D6-BranesMar 06 2008Apr 21 2009We construct the type IIA nonsupersymmetric meta-stable brane configurations corresponding to the various N=1 supersymmetric gauge theories. The D6-branes are both displaced and rotated where these deformations are described as the mass term and quartic ... More
Meta-Stable Brane Configurations of Triple Product Gauge GroupsAug 31 2007Apr 21 2009From an N=1 supersymmetric electric gauge theory with the gauge group SU(N_c) x SU(N_c') x SU(N_c'') with fundamentals for each gauge group and the bifundamentals, we apply Seiberg dual to each gauge group and obtain the N=1 supersymmetric dual magnetic ... More
Meta-Stable Brane Configurations with Seven NS5-BranesAug 03 2007Mar 21 2008We present the intersecting brane configurations consisting of NS-branes, D4-branes(and anti D4-branes) and O6-plane, of type IIA string theory corresponding to the meta-stable nonsupersymmetric vacua in four dimensional N=1 supersymmetric SU(N_c) x SU(N_c') ... More
Meta-Stable Brane Configurations by Adding an Orientifold-Plane to Giveon-KutasovJun 01 2007Aug 01 2007In hep-th/0703135, they have found the type IIA intersecting brane configuration where there exist three NS5-branes, D4-branes and anti-D4-branes. By analyzing the gravitational interaction for the D4-branes in the background of the NS5-branes, the phase ... More
Penrose Limit of AdS_4 x N^{0,1,0} and N=3 Gauge TheoryJun 19 2002Sep 05 2002We consider M-theory on AdS_4 x N^{0,1,0} where N^{0,1,0}= (SU(3) x SU(2))/(SU(2) x U(1)). We review a Penrose limit of AdS_4 x N^{0,1,0} that provides the pp-wave geometry of AdS_4 x S^7. There exists a subsector of three dimensional N=3 dual gauge theory, ... More
Penrose Limit of AdS_4 x V_{5,2} and Operators with Large R ChargeJun 04 2002Oct 17 2002We consider M-theory on AdS_4 x V_{5,2} where V_{5,2}= SO(5)/SO(3) is a Stiefel manifold. We construct a Penrose limit of AdS_4 x V_{5,2} that provides the pp-wave geometry. There exists a subsector of three dimensional N=2 dual gauge theory, by taking ... More
The Primary Spin-4 Casimir Operators in the Holographic SO(N) Coset Minimal ModelsFeb 01 2012May 14 2012Starting from SO(N) current algebra, we construct two lowest primary higher spin-4 Casimir operators which are quartic in spin-1 fields. For N is odd, one of them corresponds to the current in the WB_{\frac{N-1}{2}} minimal model. For N is even, the other ... More
Geometry, D-Branes and N=1 Duality in Four Dimensions IIMay 02 1997We study N=1 dualities in four dimensional supersymmetric gauge theories in terms of wrapping D 6-branes around 3-cycles of Calabi-Yau threefolds in type IIA string theory. We generalize the recent work of geometrical realization for the models which ... More
Explicit Construction of $N=2$ $W_3$ Current in the $N=2$ Coset $\frac{SU(3)}{SU(2) \times U(1)}$ ModelOct 22 1994Oct 25 1994We discuss the nonlinear extension of $N=2$ superconformal algebra by generalizing Sugawara construction and coset construction built from $N=2$ currents based on Kazama-Suzuki $N=2$ coset model $\frac{SU(3)}{SU(2) \times U(1)}$ in $N=2$ superspace. For ... More
Muon-spin-relaxation study of the magnetic penetration depth in MgB2Aug 27 2001The magnetic vortex lattice (VL) of polycrystalline MgB2 has been investigated by transverse-field muon-spin-relaxation (TF-MuSR). The evolution of TF-MuSR depolarization rate, sigma, that is proportional to the second moment of the field distribution ... More
Calculation of permittivity tensors for invisibility devices by effective medium approach in general relativityJul 01 2010Apr 11 2011Permittivity tensors of arbitrary shaped invisibility devices are obtained using effective medium approach in general relativity. As special cases, analytical expressions for the permittivity tensors of invisibility cloaks for the elliptic cylinder, prolate ... More
Black hole state evolution and Hawking radiationJun 11 2010Nov 09 2010The effect of a black hole state evolution on the Hawking radiation is studied using the final state boundary condition. It is found that theormodynamic or statistical mechanical properties of a black hole depend strongly on the unitary evolution operator ... More