Results for "D. W. Song"

total 169938took 0.14s
Predictions for cross sections of light proton-rich isotopes in $^{40}$Ca + $^{9}$Be reactionApr 26 2018The cross sections for the $Z=$ 10 -- 19 with isotopes $T_{z}=-3/2$ to $-5$ in the 140$A$ MeV $^{40}$Ca + $^{9}$Be projectile fragmentation reaction have been predicted. An empirical formula based on the correlation between the cross section and average ... More
Pulsar Velocity with Three-Neutrino Oscillations in Non-adiabatic ProcessesOct 01 1997We have studied the position dependence of neutrino energy on the Kusenko-Segr\`{e} mechanism as an explanation of the proper motion of pulsars. The mechanism is also examined in three-generation mixing of neutrinos and in a non-adiabatic case. The position ... More
Automorphic Forms, Bundles and Yang-Mills EquationsMay 13 1997Nov 22 2001The paper has been withdrawn by the author.
The P versus NP Problem in Quantum PhysicsFeb 12 2014Motivated by the fact that information is encoded and processed by physical systems, the P versus NP problem is examined in terms of physical processes. In particular, we consider P as a class of deterministic, and NP as nondeterministic, polynomial-time ... More
Einstein's MoonAug 15 2010Apr 16 2013An account of the subjective elements of quantum mechanics or of whether, as Einstein famously asked, the Moon exists when nobody is looking at it.
Raman scattering study of NaFe$_{0.53}$Cu$_{0.47}$AsApr 23 2018Sep 14 2018We use polarization-resolved Raman scattering to study lattice dynamics in NaFe$_{0.53}$Cu$_{0.47}$As single crystals. We identify 4 $A_{1g}$ phonon modes at 125, 172, 183 and 197 cm$^{-1}$, and 4 $B_{3g}$ phonon modes at 101, 138, 173, 226 cm$^{-1}$. ... More
Large-scale solar cycle features of solar photospheric magnetic fieldMay 14 2007It is well accepted that the solar cycle originates from a magnetohydrodynamics dynamo deep inside the Sun. Many dynamo models have long been proposed based on a lot of observational constraints. In this paper, using 342 NSO/Kitt Peak solar synoptic charts ... More
On the Cardinality of Positively Linearly Independent SetsSep 24 2015Positive bases, which play a key role in understanding derivative free optimization methods that use a direct search framework, are positive spanning sets that are positively linearly independent. The cardinality of a positive basis in $\R^n$ has been ... More
Superconductivity in CaSn3 single crystal with a AuCu3-type structureNov 20 2015We report the superconductivity of the CaSn3 single crystal with a AuCu3-type structure, namely cubic space group Pm3m. The superconducting transition temperature TC=4.2 K is determined by the magnetic susceptibility, electrical resistivity, and heat ... More
Intrinsic Instability of Coronal StreamersJun 01 2009Plasma blobs are observed to be weak density enhancements as radially stretched structures emerging from the cusps of quiescent coronal streamers. In this paper, it is suggested that the formation of blobs is a consequence of an intrinsic instability ... More
Fermi arc induced vortex structure in Weyl beam shiftsSep 10 2018Dec 20 2018In periodic media, despite the close relationship between geometrical effects in the bulk and topological surface states, the two are typically probed separately. We show that when beams in a Weyl medium reflect off an interface with a gapped medium, ... More
Large-basis shell model studies of light nuclei with a multi-valued G-matrix effective interactionJul 07 1995Large-basis shell model studies of low-lying excitations in light nuclei from 4He to 7Li have been performed with a multi-valued G-matrix effective interaction, as recently suggested by Haxton et al.. Calculations were performed relative to the vacuum ... More
Photo-transmutation of long-lived radionuclide Cs-135 by laser-plasma driven electron sourceJan 13 2016Relativistic electrons, accelerated by the laser ponderomotive force, can be focused onto a high-Z convertor to generate high-brightness beams of gamma-rays, which in turn can be used to induce photonuclear reactions. In this work, the possibility of ... More
Topological Valley Currents in Gapped Dirac MaterialsDec 04 2014Gapped 2D Dirac materials, in which inversion symmetry is broken by a gap-opening perturbation, feature a unique valley transport regime. The system ground state hosts dissipationless persistent valley currents existing even when topologically protected ... More
Quasi-Periodic Releases of Streamer Blobs and Velocity Variability of the Slow Solar Wind near the SunJul 05 2009We search for persistent and quasi-periodic release events of streamer blobs during 2007 with the Large Angle Spectrometric Coronagraph on the \textit{Solar and Heliospheric Observatory} and assess the velocity of the slow solar wind along the plasma ... More
Multiplicity scaling in ideal and viscous hydrodynamicsMay 13 2008Jul 03 2008Using numerical results from ideal and viscous relativistic hydrodynamic simulations with three different equations of state, for Au+Au and Cu+Cu collisions at different centralities and initial energy densities, we explore the dependence of the eccentricity-scaled ... More
Viscous hydrodynamics with bulk viscosity -- uncertainties from relaxation time and initial conditionsJul 14 2009Sep 22 2009Bulk viscosity suppresses elliptic flow v_2, as does shear viscosity. It can thus not be neglected when extracting the shear viscosity from elliptic flow data. We here explore uncertainties in the bulk viscous contribution to viscous v_2 suppression that ... More
Suppression of elliptic flow in a minimally viscous quark-gluon plasmaSep 05 2007Dec 21 2007We compute the time evolution of elliptic flow in non-central relativistic heavy-ion collisions, using a (2+1)-dimensional code with longitudinal boost-invariance to simulate viscous fluid dynamics in the causal Israel-Stewart formulation. We show that ... More
Causal relativistic hydrodynamics for viscous fluidsJun 02 2008Jun 03 2008We report on recent results from VISH2+1, a code that solves the relativistic Israel-Stewart equations for causal viscous hydrodynamics for heavy-ion collisions with longitudinal boost invariance. We find that even ``minimal'' shear viscosity eta/s=hbar/(4pi) ... More
Dynamics of a tight-binding ring threaded by time-periodic magnetic fluxMay 11 2011Oct 04 2011We analytically study the effects of periodically alternating magnetic fields on the dynamics of a tight-binding ring. It is shown that an arbitrary quantum state can be frozen coherently at will by the very frequent square-wave field as well as the monochromatic-wave ... More
Direct Experimental Observation of the Gas Filamentation Effect using a Two-bunch X-ray FEL BeamMay 28 2017We report the experimental observation of the filamentation effect in gas devices designed for X-ray Free-electron Lasers. The measurements were carried out at the Linac Coherent Light Source on the X-ray Correlation Spectroscopy (XCS) instrument using ... More
Extracting the QGP viscosity from RHIC data -- a status report from viscous hydrodynamicsDec 22 2008Jan 29 2009We report recent progress on causal viscous hydrodynamics for relativistic heavy ion collisions. For fixed specific shear viscosity eta/s, uncertainties in the elliptic flow arising from initial conditions, equation of state, bulk viscosity and numerical ... More
How to Evolve Safe Control StrategiesAug 03 2002Autonomous space vehicles need adaptive control strategies that can accommodate unanticipated environmental conditions. The evaluation of new strategies can often be done only by actually trying them out in the real physical environment. Consequently, ... More
Interplay of shear and bulk viscosity in generating flow in heavy-ion collisionsSep 08 2009Sep 08 2009We perform viscous hydrodynamic calculations in 2+1 dimensions to investigate the influence of bulk viscosity on the viscous suppression of elliptic flow in non-central heavy-ion collisions at RHIC energies. Bulk and shear viscous effects on the evolution ... More
Causal viscous hydrodynamics in 2+1 dimensions for relativistic heavy-ion collisionsDec 21 2007May 20 2008We explore the effects of shear viscosity on the hydrodynamic evolution and final hadron spectra of Cu+Cu collisions at ultrarelativistic collision energies, using the newly developed (2+1)-dimensional viscous hydrodynamic code VISH2+1. Based on the causal ... More
Design of a Peanut Hohlraum with Low Gas-Fill Density for the Laser MegajouleJun 07 2017Recent experiments on the National Ignition Facility [D.E. Hinkel et al., Phys. Rev. Lett. 117, 225002 (2016)] demonstrates that utilizing a long, large case-to-capsule ratio (=3) conventional cylindrical hohlraum at moderate gas-fill density (=0.6 mg/cm3 ... More
Quasi-particle scattering and protected nature of topological states in a parent topological insulator Bi$_2$Se$_3$Dec 19 2009We report on angle resolved photoemission spectroscopic studies on a parent topological insulator (TI), Bi$_2$Se$_3$. The line width of the spectral function (inverse of the quasi-particle lifetime) of the topological metallic (TM) states shows an anomalous ... More
Raman scattering investigation of quasi-one-dimensional superconductor Ta$_{4}$Pd$_{3}$Te$_{16}$May 20 2015We have performed polarized Raman scattering measurements on the newly discovered superconductor Ta$_{4}$Pd$_{3}$Te$_{16}$ ($T_c = 4.6$ K). We observe twenty-eight out of thirty-three Raman active modes, with frequencies in good accordance with first-principles ... More
Spin-orbit coupling enhanced superconductivity in Bi-rich compounds ABi$_{3}$ (A=Sr and Ba)Oct 19 2015Recently, Bi-based compounds have attracted attentions because of the strong spin-orbit coupling (SOC). In this work, we figured out the role of SOC in ABi$_{3}$ (A=Sr and Ba) by theoretical investigation of the band structures, phonon properties, and ... More
Information Erasure and the Generalized Second Law of Black Hole ThermodynamicsSep 25 2000We consider the generalized second law of black hole thermodynamics in the light of quantum information theory, in particular information erasure and Landauer's principle (namely, that erasure of information produces at least the equivalent amount of ... More
Entanglement Swapping Chains for General Pure StatesJun 29 2000We consider entanglement swapping schemes with general (rather than maximally) entangled bipartite states of arbitary dimension shared pairwise between three or more parties in a chain. The intermediate parties perform generalised Bell measurements with ... More
Quantum Anti-CloningJan 28 2000Feb 25 2000We derive the transformation for the optimal universal quantum anti-cloner which produces two anti-parallel outputs for a single input state. The fidelity is shown to be 2/3 which is same as the measurement fidelity. We consider a probabilistic quantum ... More
Hysteresis in a Superfluid Atom CircuitDec 09 2014May 09 2016The energy band structure of a rotating BEC with a link in a quasi-one-dimensional torus and the role of dissipation is studied. Through this study we are able to give a microscopic interpretation of hysteresis recently observed in the experiment and ... More
Streamer Wave Events Observed in Solar Cycle 23May 22 2011In this paper we conduct a data survey searching for well-defined streamer wave events observed by the Large Angle and Spectrometric Coronagraph (LASCO) on-board the Solar and Heliospheric Observatory (SOHO) throughout Solar Cycle 23. As a result, 8 candidate ... More
Heavy flavor in relativistic heavy-ion collisionsAug 17 2015We study charm production in ultra-relativistic heavy-ion collisions by using the Parton-Hadron-String Dynamics (PHSD) transport approach. The initial charm quarks are produced by the PYTHIA event generator tuned to fit the transverse momentum spectrum ... More
A coronal seismological study with streamer wavesDec 23 2010We present a novel method to evaluate the Alfven speed and the magnetic field strength along the streamer plasma sheet in the outer corona. The method is based on recent observations of streamer waves, which are regarded as the fast kink body mode carried ... More
Raman study of lattice dynamics in Weyl semimetal TaAsJun 15 2015We report a polarized Raman study of Weyl semimetal TaAs. We observe all the optical phonons, with energies and symmetries consistent with our first-principles calculations. We detect additional excitations assigned to multiple-phonon excitations. These ... More
Universal Manipulation of a Single QubitAug 02 2000We find the optimal universal way of manipulating a single qubit, |psi(theta,phi)>, such that (theta,phi)->(theta-k,phi-l). Such optimal transformations fall into two classes. For 0 =< k =< pi/2 the optimal map is the identity and the fidelity varies ... More
CP Phases in Correlated Production and Decay of Neutralinos in the Minimal Supersymmetric Standard ModelJul 23 1999Jul 24 1999We investigate the associated production of neutralinos $e^+e^-\to\tilde{\chi}^0_1\tilde{\chi}^0_2$ accompanied by the neutralino leptonic decay $\tilde{\chi}^0_2\to\tilde{\chi}^0_1 \ell^+\ell^-$, taking into account initial beam polarization and production-decay ... More
Nonlinear Qubit TransformationsFeb 20 2001Jun 17 2001We generalise our previous results of universal linear manipulations [Phys. Rev. A63, 032304 (2001)] to investigate three types of nonlinear qubit transformations using measurement and quantum based schemes. Firstly, nonlinear rotations are studied. We ... More
No Signalling and Probabilistic Quantum CloningMay 07 1999We show that the condition of no faster-than-light signalling restricts the number of quantum states that can be cloned in a given Hilbert space. This condition leads to the constraints on a probabilistic quantum cloning machine (PQCM) recently found ... More
CuSe-based layered compound Bi$_{2}$YO$_{4}$Cu$_{2}$Se$_{2}$ as a quasi-two-dimensional metalMar 31 2014May 30 2014We have investigated the physical properties of a new layered oxyselenide Bi$_{2}$YO$_{4}$Cu$_{2}$Se$_{2}$, which crystallizes in an unusual intergrowth structure with Cu$_{2}$Se$_{2}$ and Bi$_{2}$YO$_{4}$ layers. Electric transport measurement indicates ... More
Mechanisms of weak thickness dependence of the critical current density in strong pinning ex situ metal-organic-deposition route YBa2Cu3O7-x coated conductorsMay 24 2006We report on the thickness dependence of the superconducting characteristics including critical current Ic, critical current density Jc, transition temperature Tc, irreversibility field Hirr, bulk pinning force plot Fp(H), and the normal state resistivity ... More
Probing hyperbolic polaritons using infrared attenuated total reflectance micro-spectroscopyOct 01 2018Hyperbolic polariton modes are highly appealing for a broad range of applications in nanophotonics, including surfaced enhanced sensing, sub-diffractional imaging and reconfigurable metasurfaces. Here we show that attenuated total reflectance micro-spectroscopy ... More
Finite temperature effects on the neutrino decoupling in the early UniverseFeb 13 1997Leading finite temperature effects on the neutrino decoupling temperature in the early Universe have been studied. We have incorporated modifications of the dispersion relation and the phase space distribution due to the presence of particles in the heat ... More
Energy Flows in Graphene: Hot Carrier Dynamics and CoolingOct 20 2014Long lifetimes of hot carriers can lead to qualitatively new types of responses in materials. The magnitude and time scales for these responses reflect the mechanisms governing energy flows. We examine the microscopics of two processes which are key for ... More
Energy-driven Drag at Charge Neutrality in GrapheneMay 23 2012Coulomb coupling between proximal layers in graphene heterostructures results in efficient energy transfer between the layers. We predict that, in the presence of correlated density inhomogeneities in the layers, vertical energy transfer has a strong ... More
Beyond the Shell Model: The Canonical Nuclear Many-Body Problem as an Effective TheoryJul 24 1999We describe a strategy for attacking the canonical nuclear structure problem ---bound-state properties of a system of point nucleons interacting via a two-body potential---which involves an expansion in the number of particles scattering at high momenta, ... More
Dynamical Mean Field Study of the Two-Dimensional Disordered Hubbard ModelJul 05 2007Jan 28 2008We study the two-dimensional paramagnetic Anderson-Hubbard model using an extension of dynamical mean-field theory that allows us to treat disorder and strong electronic correlations on equal footing. We investigate the scaling of the inverse participation ... More
Spectra and elliptic flow for identified hadrons in 2.76 A TeV Pb+Pb collisionsNov 01 2013Jan 23 2014Using the VISHNU hybrid model that couples (2+1)-dimensional viscous hydrodynamics to a microscopic hadronic transport model, we calculate the multiplicity, p_T spectra and elliptic flow for pions, kaons, and protons in 2.76 A TeV Pb+Pb collisions, using ... More
Giant Hall photoconductivity in narrow-gapped Dirac materialsDec 15 2016Carrier dynamics acquire a new character in the presence of Bloch-band Berry curvature, which naturally arises in gapped Dirac materials (GDMs). Here we argue that photoresponse in GDMs with small band gaps is dramatically enhanced by Berry curvature. ... More
Plasmon geometric phase and plasmon Hall shiftOct 19 2017The collective plasmonic modes of a metal comprise a pattern of charge density and tightly-bound electric fields that oscillate in lock-step to yield enhanced light-matter interaction. Here we show that metals with non-zero Hall conductivity host plasmons ... More
The viscosity of quark-gluon plasma at RHIC and the LHCAug 26 2011The specific shear viscosity (eta/s)_QGP of quark-gluon plasma (QGP) can be extracted from elliptic flow data in heavy-ion collisions by comparing them with the dynamical model VISHNU which couples a viscous fluid dynamic description of the QGP with a ... More
The geometrically-averaged density of states as a measure of localizationSep 22 2006Jun 22 2007Motivated by current interest in disordered systems of interacting electrons, the effectiveness of the geometrically averaged density of states, $\rho_g(\omega)$, as an order parameter for the Anderson transition is examined. In the context of finite-size ... More
The geometrically-averaged density of states calculated from the local Green's function as a measure of localizationSep 05 2007With the goal of measuring localization in disordered interacting systems, we examine the finite-size scaling of the geometrically-averaged density of states calculated from the local Green's function with finite energy resolution. Our results show that, ... More
A Study of Off-Forward Parton DistributionsFeb 21 1997Feb 27 1997An extensive theoretical analysis of off-forward parton distributions (OFPDs) is presented. The OFPDs and the form factors of the quark energy-momentum tensor are estimated at a low-energy scale using a bag model. Relations among the second moments of ... More
Fermi arc plasmons in Weyl semimetalsJan 31 2017In the recently discovered Weyl semimetals, the Fermi surface may feature disjoint, open segments -- the so-called Fermi arcs -- associated with topological states bound to exposed crystal surfaces. Here we show that the collective dynamics of electrons ... More
XMCD characterization of rare-earth dopants in Ni$_{81}$Fe$_{19}$(50nm): microscopic basis of engineered dampingMar 25 2004We present direct evidence for the contribution of local orbital moments to the damping of magnetization precession in magnetic thin films. Using x-ray magnetic circular dichroism (XMCD) characterization of rare-earth (RE) M$_{4,5}$ edges in Ni$_{81}$Fe$_{19}$ ... More
Breakdown of single spin-fluid model in heavily hole-doped superconductor CsFe2As2May 28 2017Although Fe-based superconductors are multiorbital correlated electronic systems, previous nuclei magnetic resonance (NMR) measurement suggests that a single spin-fluid model is sufficient to describe its spin behavior. Here, we firstly observed the breakdown ... More
Berryogenesis: self-induced Berry flux and spontaneous non-equilibrium magnetismJul 04 2018Spontaneous symmetry breaking is central to the description of interacting phases of matter. Here we reveal a new mechanism through which a driven interacting system subject to a time-reversal symmetric driving field can spontaneously magnetize. We show ... More
Chiral plasmons without magnetic fieldJun 15 2015May 23 2016Plasmons, the collective oscillations of interacting electrons, possess emergent properties that dramatically alter the optical response of metals. We predict the existence of a new class of plasmons -- chiral Berry plasmons (CBPs) -- for a wide range ... More
Hall Drag and Magnetodrag in GrapheneMar 14 2013Sep 19 2013Massless Dirac fermions in graphene at charge neutrality form a strongly interacting system in which both charged and neutral (energy) modes play an important role. These modes are essentially decoupled in the absence of a magnetic field, but become strongly ... More
Electron quantum metamaterials in van der Waals heterostructuresNov 08 2018In recent decades, scientists have developed the means to engineer synthetic periodic arrays with feature sizes below the wavelength of light. When such features are appropriately structured, electromagnetic radiation can be manipulated in unusual ways, ... More
Symmetry, spin-texture, and tunable quantum geometry in a WTe$_2$ monolayerMay 02 2018Jan 02 2019The spin orientation of electronic wavefunctions in crystals is an internal degree of freedom, typically insensitive to electrical knobs. We argue from a general symmetry analysis and a $\vec k \cdot \vec p$ perspective, that monolayer 1T'-WTe$_2$ possesses ... More
Large optical conductivity of Dirac semimetal Fermi arc surfaces statesMay 03 2017Fermi arc surface states, a hallmark of topological Dirac semimetals, can host carriers that exhibit unusual dynamics distinct from that of their parent bulk. Here we find that Fermi arc carriers in intrinsic Dirac semimetals possess a strong and anisotropic ... More
Proof of a recent conjecture of Z.-W. SunApr 18 2016The polynomials $d_n(x)$ are defined by \begin{align*} d_n(x) &= \sum_{k=0}^n{n\choose k}{x\choose k}2^k. \end{align*} We prove that, for any prime $p$, the following congruences hold modulo $p$: \begin{align*} \sum_{k=0}^{p-1}\frac{{2k\choose k}}{4^k} ... More
A recursive algorithm for trees and forestsFeb 06 2017Trees or rooted trees have been generously studied in the literature. A forest is a set of trees or rooted trees. Here we give recurrence relations between the number of some kind of rooted forest with $k$ roots and that with $k+1$ roots on $\{1,2,\ldots,n\}$. ... More
Low-dissipation edge currents without edge statesMay 15 2018We show that bulk free carriers in topologically trivial multi-valley insulators with non-vanishing Berry curvature give rise to low-dissipation edge currents, which are squeezed within a distance of the order of the valley diffusion length from the edge. ... More
Long-lived domain wall plasmons in gapped bilayer grapheneJun 02 2017Topological domain walls in dual-gated gapped bilayer graphene host edge states that are gate- tunable and valley polarized. Here we predict that plasmonic collective modes can propagate along these topological domain walls even at zero bulk density, ... More
Shockley-Ramo theorem and long-range photocurrent response in gapless materialsDec 23 2011Jan 03 2015Scanning photocurrent maps of gapless materials, such as graphene, often exhibit complex patterns of hot spots positioned far from current-collecting contacts. We develop a general framework that helps to explain the unusual features of the observed patterns, ... More
A New Scale-Dependent Cosmology with the Generalized Robertson--Walker Metric and Einstein EquationDec 07 1994Jan 25 1995Based on the observed increase of $\Omega _0$ as a function of cosmic scale, the Robertson--Walker metric and the Einstein equation are generalized so that $ \Omega_0$, $H_0$, and the age of the Universe, $t_0$, all become functions of cosmic scales at ... More
Effects of the Running Gravitational Constant on the Amount of Dark MatterJan 19 1995The amount of dark matter in the Milky Way and beyond is examined by taking into account the possible running of the gravitational constant $G$ as a function of distance scale. If the running of $G$, as suggested by the Asymptotically-Free Higher-Derivative ... More
The Canonical Nuclear Many-Body Problem as a Rigorous Effective TheoryJun 27 1999The shell model is the standard tool for addressing the canonical nuclear many-body problem of nonrelativistic nucleons interacting through a static potential. We discuss several of the uncontrolled approximations that are made in this model to motivate ... More
Spin relaxation of conduction electrons in bulk III-V semiconductorsNov 06 2001Nov 25 2001Spin relaxation time of conduction electrons through the Elliot-Yafet, D'yakonov-Perel and Bir-Aronov-Pikus mechanisms is calculated theoretically for bulk GaAs, GaSb, InAs and InSb of both $n$- and $p$-type. Relative importance of each spin relaxation ... More
Dynamics of one-dimensional tight-binding models with arbitrary time-dependent external homogeneous fieldsMay 31 2012Jul 08 2012The exact propagators of two one-dimensional systems with time-dependent external fields are presented by following the path-integral method. It is shown that the Bloch acceleration theorem can be generalized to the impulse-momentum theorem in quantum ... More
Effects of Magnetovolume and Spin-orbit Coupling in the Ferromagnetic Cubic Perovskite BaRuO3Jul 31 2012Apr 24 2013BaRuO3 having five different crystal structures has been synthesized by varying the pressure while sintering. Contrary to the other phases being nonmagnetic, the cubic perovskite phase synthesized recently shows an itinerant ferromagnetic character. We ... More
Robustness of topological states to lattice instability in non-symmorphic topological insulator KHgSbFeb 28 2017We report a polarized Raman scattering study of non-symmorphic topological insulator KHgSb with hourglass-like electronic dispersion. Supported by theoretical calculations, we show that the lattice of the previously assigned space group $P6_3/mmc$ (No. ... More
New phase transition in Na$_{2}$Ti$_{2}$As$_{2}$O revealed by Raman scatteringJan 08 2016We performed a Raman scattering study of Na$_2$Ti$_2$As$_2$O. We identified a symmetry breaking structural transition at around $T_s = 150$ K, which matches a large bump in the electrical resistivity. Several new peaks are detected below that transition. ... More
The Spitzer Atlas of Stellar SpectraOct 27 2010We present the Spitzer Atlas of Stellar Spectra (SASS), which includes 159 stellar spectra (5 to 32 mic; R~100) taken with the Infrared Spectrograph on the Spitzer Space Telescope. This Atlas gathers representative spectra of a broad section of the Hertzsprung-Russell ... More
The Effects of Post-Thermal Annealing on the Emission Spectra of GaAs/AlGaAs Quantum Dots grown by Droplet EpitaxyAug 22 2012We fabricated GaAs/AlGaAs quantum dots by droplet epitaxy method, and obtained the geometries of the dots from scanning transmission electron microscopy data. Post-thermal annealing is essential for the optical activation of quantum dots grown by droplet ... More
Large orbital moment and spin-orbit enabled Mott transition in the Ising Fe honeycomb lattice BaFe2(PO4)2Jun 03 2015Sep 07 2015BaFe2(PO4)2 is an unusual Ising insulating ferromagnet based on the Fe$^{2+}$ spin $S$ = 2 ion, the susceptibility of which suggests a large orbital component to the Fe local moment. We apply density functional theory based methods to obtain a microscopic ... More
Single crystal growth and characterizations of Cu0.03TaS2 superconductorsAug 18 2008Dec 23 2008Single crystal of Cu0.03TaS2 with low copper intercalated content was successfully grown via chemical iodine-vapor transport. The structural characterization results show that the copper intercalated 2H-Cu0.03TaS2 single crystal has the same structure ... More
Superconductivity and single crystal growth of Ni0:05TaS2Nov 16 2008Jul 10 2009Superconductivity was discovered in a Ni0:05TaS2 single crystal. A Ni0:05TaS2 single crystal was successfully grown via the NaCl/KCl flux method. The obtained lattice constant c of Ni0:05TaS2 is 1.1999 nm, which is significantly smaller than that of 2H-TaS2 ... More
Energy dependence of the spin excitation anisotropy in uniaxial-strained BaFe1.9Ni0.1As2Nov 09 2015We use inelastic neutron scattering to study the temperature and energy dependence of the spin excitation anisotropy in uniaxial-strained electron-doped iron pnictide BaFe$_{1.9}$Ni$_{0.1}$As$_2$ near optimal superconductivity ($T_c=20$ K). Our work has ... More
Observation of a pressure-induced transition from interlayer ferromagnetism to intralayer antiferromagnetism in Sr4Ru3O10Jun 22 2018Sr4Ru3O10 is a Ruddlesden-Popper compound with triple Ru-O perovskite layers separated by Sr-O alkali layers. This compound presents a rare coexistence of interlayer (c-axis) ferromagnetism and intralayer (basal-plane) metamagnetism at ambient pressure. ... More
Poincaré inequality and exponential integrability of hitting times for linear diffusionsJul 04 2009Let $X$ be a regular linear continuous positively recurrent Markov process with state space $\R$, scale function $S$ and speed measure $m$. For $a\in \R$ denote B^+_a&=\sup_{x\geq a} \m(]x,+\infty[)(S(x)-S(a)) B^-_a&=\sup_{x\leq a} \m(]-\infty;x[)(S(a)-S(x)) ... More
Domain wall motion in epitaxial Pb(Zr,Ti)O3 capacitors investigated by modified piezoresponse force microscopyMay 21 2008We investigated the time-dependent domain wall motion of epitaxial PbZr0.2Ti0.8O3 capacitors 100 nm-thick using modified piezoresponse force microscopy (PFM). We obtained successive domain evolution images reliably by combining the PFM with switching ... More
Polarization Switching Dynamics Governed by Thermodynamic Nucleation Process in Ultrathin Ferroelectric FilmsMay 03 2006A long standing problem of domain switching process - how domains nucleate - is examined in ultrathin ferroelectric films. We demonstrate that the large depolarization fields in ultrathin films could significantly lower the nucleation energy barrier (U*) ... More
Single-filament Composite MgB2/SUS Ribbons by Powder-In-Tube ProcessJun 07 2001We report the successful fabrication of single-filament composite MgB2/SUS ribbons, as an ultra-robust conductor type, employing the powder-in-tube (PIT) process, by swaging and cold rolling only. The remarkable transport critical current (Ic) of the ... More
Polarization Relaxation Induced by Depolarization Field in Ultrathin Ferroelectric BaTiO$_3$ CapacitorsJun 20 2005Oct 14 2005Time-dependent polarization relaxation behaviors induced by a depolarization field $E_{d}$ were investigated on high-quality ultrathin SrRuO$_{3}$/BaTiO$_{3}$/SrRuO$_{3}$ capacitors. The $E_d$ values were determined experimentally from an applied external ... More
Epitaxial growth of multiferroic Pb(Zr0.57Ti0.43)O3-Pb(Fe2/3W1/3)O3 solid-solution thin films and their magnetoelectric effectsJan 27 2010We report on epitaxial growth of single-phase [Pb(Zr0.57Ti0.43)O3]0.8[Pb(Fe2/3W1/3)O3]0.2 (PZT-PFW) solid-solution thin films using pulsed laser deposition. X-ray diffraction measurements reveal that the films have a tetragonal structure. The films exhibit ... More
Electron doping evolution of the neutron spin resonance in NaFe$_{1-x}$Co$_{x}$AsMay 23 2016Neutron spin resonance, a collective magnetic excitation coupled to superconductivity, is one of the most prominent features shared by a broad family of unconventional superconductors including copper oxides, iron pnictides, and heavy fermions. In this ... More
Spitzer/MIPS Observations of Stars in the Beta Pictoris Moving GroupMar 11 2008We present Multiband Imaging Photometer for Spitzer (MIPS) observations at 24 and 70 microns for 30 stars, and at 160 microns for a subset of 12 stars, in the nearby (~30 pc), young (~12 Myr) Beta Pictoris Moving Group (BPMG). In several cases, the new ... More
X-raying the Intergalactic OVI AbsorbersDec 10 2008Mar 23 2009The observed intergalactic OVI absorbers at z>0 have been regarded as a significant reservoir of the ``missing baryons''. However, to fully understand how these absorbers contribute to the baryon inventory, it is crucial to determine whether the systems ... More
Warm-Hot Gas in and around the Milky Way: Detection and Implications of OVII Absorption toward LMC X-3Aug 30 2005X-ray absorption lines of highly-ionized species such as OVII at about zero redshift have been firmly detected in the spectra of several active galactic nuclei. However, the location of the absorbing gas remains a subject of debate. To separate the Galactic ... More
Complex Monge Ampere EquationsSep 11 2012Oct 01 2012This is a survey of some of the recent developments in the theory of complex Monge-Ampere equations. The topics discussed include refinements and simplifications of classical a priori estimates, methods from pluripotential theory, variational methods ... More
Multimodal Image Denoising based on Coupled Dictionary LearningJun 26 2018In this paper, we propose a new multimodal image denoising approach to attenuate white Gaussian additive noise in a given image modality under the aid of a guidance image modality. The proposed coupled image denoising approach consists of two stages: ... More
Construction of the Korean VLBI Network (KVN)Dec 30 2004Korea's new VLBI project to construct the Korean VLBI Network (KVN) started in 2001, as a 7-year project that is fully funded by our government. We plan to build 3 new high-precision radio telescopes of 21-m diameter in 3 places in Korea, which will be ... More
XMM-Newton detection of two clusters of galaxies with strong SPT Sunyaev-Zel'dovich effect signaturesMar 15 2010We report on the discovery of two galaxy clusters, SPT-CL J2332-5358 and SPT-CL J2342-5411, in X-rays. These clusters were also independently detected through their Sunyaev-Zel'dovich effect by the South Pole Telescope, and confirmed in the optical band ... More
Transport and anisotropy in single-crystalline SrFe$_2$As$_2$ and $A_{0.6}$K$_{0.4}$Fe$_2$As$_2$ ($A$ = Sr, Ba) superconductorsJun 16 2008Nov 21 2008We have successfully grown high quality single crystals of SrFe$_2$As$_2$ and A$_{0.6}$K$_{0.4}$Fe$_2$As$_2$(A=Sr, Ba) using flux method. The resistivity, specific heat and Hall coefficient have been measured. For parent compound SrFe$_2$As$_2$, an anisotropic ... More