Results for "S. Kasahara"

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Geometric intersection in representations of mapping class groups of surfacesApr 13 2015Dec 12 2016We show that the detection of geometric intersection in an arbitrary representation of the mapping class group of surface implies the injectivity of that representation up to center, and vice versa. As an application, we discuss the geometric intersection ... More
Addendum to: "An expansion of the Jones representation of genus 2 and the Torelli group"Apr 07 2010Apr 19 2010We observe that the determinant of the representation provides a little restriction for the structure of the graded quotients $\mathcal{G}_k^Q{F}$ introduced in both [Algebr. Geom. Topol. 1 (2001) 39-55] and [J. Knot Theory Ramifications 13 (2004) 297-306] ... More
On visualization of the linearity problem for mapping class groups of surfacesFeb 29 2012Mar 05 2014We derive two types of linearity conditions for mapping class groups of orientable surfaces: one for once-punctured surface, and the other for closed surface, respectively. For the once-punctured case, the condition is described in terms of the action ... More
Unconventional thermal metallic state of charge-neutral fermions in an insulatorMay 14 2019Quantum oscillations (QOs) in transport and thermodynamic parameters at high magnetic fields are an unambiguous signature of the Fermi surface, the defining characteristic of a metal. Therefore, recent observations of QOs in insulating SmB$_6$ and YbB$_{12}$, ... More
A Study of Cosmic Ray Composition in the Knee Region using Multiple Muon Events in the Soudan 2 DetectorDec 05 1996Feb 17 1997Deep underground muon events recorded by the Soudan 2 detector, located at a depth of 2100 meters of water equivalent, have been used to infer the nuclear composition of cosmic rays in the "knee" region of the cosmic ray energy spectrum. The observed ... More
The intersection of past and future for multivariate stationary processesJan 04 2015May 23 2015We consider an intersection of past and future property of multivariate stationary processes which is the key to deriving various representation theorems for their linear predictor coefficient matrices. We extend useful spectral characterizations for ... More
Quantum Oscillations of Electrical Resistivity in an InsulatorMay 13 2019In metals, orbital motions of conduction electrons on the Fermi surface are quantized in magnetic fields, which is manifested by quantum oscillations in electrical resistivity. This Landau quantization is generally absent in insulators. Here we report ... More
Evolution of the Fermi surface of BaFe_2(As_{1-x}P_x)_2 on entering the superconducting domeOct 19 2009Using the de Haas-van Alphen effect we have measured the evolution of the Fermi surface of BaFe_2(As_{1-x}P_x)_2 as function of isoelectric substitution (As/P) for 0.41<x<1 (T_c up to 25 K). We find that the volume of electron and hole Fermi surfaces ... More
Comparison of 3-Dimensional and 1-Dimensional Schemes in the calculation of Atmospheric NeutrinosMar 30 2001Jun 04 2001A 3-dimensional calculation of atmospheric neutrinos flux is presented, and the results are compared with those of a 1-dimensional one. In this study, interaction and propagation of particles is treated in a 3-dimensional way including the curvature of ... More
Mechanism of Fermi Level Pinning at Metal/Germanium InterfacesAug 18 2011The physical origin of Fermi level pinning (FLP) at metal/Ge interfaces has been argued over a long period. Using the Fe$_{3}$Si/Ge(111) heterostructure developed originally, we can explore electrical transport properties through atomically matched metal/Ge ... More
Low temperature specific heat of La_{3}Pd_{4}Ge_{4} with U_{3}Ni_{4}Si_{4}-type structureAug 01 2007Low temperature specific heat has been investigated in a novel ternary superconductor La_{3}Pd_{4}Ge_{4} with an U_{3}Ni_{4}Si_{4}-type structure consisting of the alternating BaAl_{4} (ThCr_{2}Si_{2})- and AlB$_{2}$-type layers. A comparative study with ... More
Atmospheric NeutrinosNov 03 1995Nov 06 1995The atmospheric neutrino-flux is calculated over the wide energy range from 1 GeV to 3,000 GeV for the study of neutrino-physics using the data from underground neutrino-detectors. The uncertainty of atmospheric neutrino-flux is also discussed. A brief ... More
Calculation of the Flux of Atmospheric NeutrinosMar 27 1995Sep 20 1995Atmospheric neutrino-fluxes are calculated over the wide energy range from 30 MeV to 3,000 GeV for the study of neutrino-physics using the data from underground neutrino-detectors. The atmospheric muon-flux at high altitude and at sea level is studied ... More
Study of cosmic ray interaction model based on atmospheric muons for the neutrino flux calculationNov 07 2006Jan 10 2007We have studied the hadronic interaction for the calculation of the atmospheric neutrino flux by summarizing the accurately measured atmospheric muon flux data and comparing with simulations. We find the atmospheric muon and neutrino fluxes respond to ... More
Calculation of atmospheric neutrino flux using the interaction model calibrated with atmospheric muon dataNov 14 2006Jan 10 2007Using the ``modified DPMJET-III'' model explained in the previous paper, we calculate the atmospheric neutrino flux. The calculation scheme is almost the same as HKKM04 \cite{HKKM2004}, but the usage of the ``virtual detector'' is improved to reduce the ... More
A New calculation of the atmospheric neutrino flux in a 3-dimensional schemeApr 23 2004Jun 14 2004We have revised the calculation of the flux of atmospheric neutrinos based on a 3-dimensional scheme with the realistic IGRF geomagnetic model. The primary flux model has been revised, based on the AMS and BESS observations, and the interaction model ... More
Coexisting localized and itinerant gapless excitations in a quantum spin liquid candidate 1T-TaS$_2$Mar 16 2018To reveal the nature of elementary excitations in a quantum spin liquid (QSL), we measured low temperature thermal conductivity and specific heat of 1T-TaS$_2$, a QSL candidate material with frustrated triangular lattice of spin-1/2. The nonzero temperature ... More
Highly Anisotropic Superconducting Gap in Nematically Ordered and Tetragonal Phases of FeSe$_{1-x}$S$_x$May 25 2017FeSe has a unique ground state in which superconductivity coexists with a nematic order without long-range magnetic ordering at ambient pressure. Here, to study how the pairing interaction evolves with nematicity, we measured the thermal conductivity ... More
Geometric intersection in representations of mapping class groups of surfacesApr 13 2015Apr 13 2016We show that the detection of geometric intersection in an arbitrary representation of the mapping class group of surface implies the injectivity of that representation up to center, and vice versa. As an application, we discuss the geometric intersection ... More
Remarks on the faithfulness of the Jones representationsMar 03 2008We consider the linear representations of the mapping class group of an n-punctured 2-sphere constructed by V. F. R. Jones using Iwahori-Hecke algebras of type A. We show that their faithfulness is equivalent to that of certain related Iwahori-Hecke algebra ... More
The Current Status and Prospect of the Ta ExperimentNov 07 2005Nov 19 2005The Telescope Array (TA) experiment is designed to observe cosmic-ray-induced air showers at extremely high energies. It is being deployed in a desert of Utah, USA; an array of 3 m^2 scintillation counters will be distributed over 760 km^ and 3 sets of ... More
An expansion of the Jones representation of genus 2 and the Torelli groupDec 21 2000We study the algebraic property of the representation of the mapping class group of a closed oriented surface of genus 2 constructed by VFR Jones [Annals of Math. 126 (1987) 335-388]. It arises from the Iwahori-Hecke algebra representations of Artin's ... More
Stripe quadrupole order in the nematic phase of FeSe$_{1-x}$S$_x$Oct 26 2017May 18 2018We use polarization-resolved electronic Raman spectroscopy to study charge dynamics in non-magnetic FeSe$_{1-x}$S$_x$ superconductor. We observe two features of the $XY$ quadrupole symmetry: a low-energy quasi-elastic peak (QEP) and an electronic continuum. ... More
Specific Heat Discontinuity, deltaC, at Tc in BaFe2(As0.7P0.3)2 - Consistent with Unconventional SuperconductivityMay 21 2011We report the specific heat discontinuity, deltaC/Tc, at Tc = 28.2 K of a collage of single crystals of BaFe2(As0.7P0.3)2 and compare the measured value of 38.5 mJ/molK**2 with other iron pnictide and iron chalcogenide (FePn/Ch) superconductors. This ... More
Microscopic Evidence of Direct Coupling between Magnetic and Superconducting Order Parameters in BaFe$_2$(As$_{1-x}$P$_x$)$_2$Nov 30 2011Feb 11 2012The coexistence of magnetism and superconductivity in the isovalent-P-substituted BaFe$_2$(As$_{1-x}$P$_x$)$_2$ has been investigated microscopically by $^{31}$P-NMR measurements. We found that superconducting (SC) transition occurs in a magnetic region ... More
Thermodynamic evidence for nematic phase transition at the onset of pseudogap in YBa$_2$Cu$_3$O$_y$Jun 16 2017A central issue in the quest to understand the superconductivity in cuprates is the nature and origin of the pseudogap state, which harbours anomalous electronic states such as Fermi arc, charge density wave (CDW), and $d$-wave superconductivity. A fundamentally ... More
Inter-plane resistivity of isovalent doped BaFe$_2$(As$_{1-x}$P$_x$)$_2$Feb 26 2013Temperature-dependent inter-plane resistivity, $\rho_c(T)$, was measured for the iron-based superconductor BaFe$_2$(As$_{1-x}$P$_x$)$_2$ over a broad isoelectron phosphorus substitution range from $x$=0 to $x$=0.60, from non-superconducting parent compound ... More
Thermal Conductivity of the Pyrochlore Superconductor KOs2O6: Strong Electron Correlations and Fully Gapped SuperconductivityMar 02 2006Jun 07 2006To elucidate the nature of the superconducting ground state of the geometrically frustrated pyrochlore KOs2O6 (Tc=9.6K), the thermal conductivity was measured down to low temperatures (~Tc/100). We found that the quasiparticle mean free path is strikingly ... More
Quantum vortex core and missing pseudogap in the multi-band BCS-BEC-crossover superconductor FeSeJan 26 2019FeSe is argued as a superconductor in the Bardeen-Cooper-Schrieffer Bose-Einstein-condensation crossover regime where the superconducting-gap size and the superconducting transition temperature Tc are comparable to the Fermi energy. In this regime, vortex ... More
Superconducting gap structure of BaFe_2(As_{1-x}P_{x})_2Sep 26 2014We present a study of the superconducting gap structure in the iron-pnictide series BaFe2(As1-xPx)2. By measuring the variation of the specific heat as a function of temperature and magnetic field we are able to determine the number and Fermi surface ... More
Calculation of Muon Fluxes at the Small Atmospheric DepthsDec 29 2003Precise knowledge of the hadronic interaction between primary cosmic rays and atmospheric nuclei is very important and fundamental to study atmospheric neutrinos and their oscillations. We studied hadronic interaction models using the data of primary ... More
Comparison of Atmospheric Neutrino Flux Calculations at Low EnergiesAug 07 1996We compare several different calculations of the atmospheric neutrino flux in the energy range relevant for contained neutrino interactions, and we identify the major sources of difference among the calculations. We find nothing that would affect the ... More
Contrasts in electron correlations and inelastic scattering between LiFeAs and LiFeP revealed by charge transportDec 23 2011Dec 28 2011By using high-quality single crystals, we quantitatively compare the transport properties between LiFeAs and LiFeP superconductors with compensated electron and hole carriers. The low-temperature resistivity follows the Fermi-liquid $AT^2$ dependence ... More
Large enhancement in the generation efficiency of pure spin currents in Ge using Heusler-compound Co_2FeSi electrodesNov 26 2013We show nonlocal spin transport in n-Ge based lateral spin-valve devices with highly ordered Co_2FeSi/n^+-Ge Schottky tunnel contacts. Clear spin-valve signals and Hanle-effect curves are demonstrated at low temperatures, indicating generation, manipulation, ... More
Abrupt recovery of Fermi-liquid transport by the c-axis collapse in CaFe2(As1-xPx)2 single crystalsDec 05 2010Single crystals of CaFe$_2$(As$_{1-x}$P$_x$)$_2$ are found to exhibit the tetragonal (T) to collapsed-tetragonal (cT) transition at $T_{\rm cT} \lesssim100$\,K for $x>0.05$. The c-axis shrinks by $\sim9$% below $T_{\rm cT}$, which substantially diminishes ... More
Nesting of electron and hole Fermi surfaces in non-superconducting BaFe_2P_2Apr 01 2011We report detailed measurements of the de Haas-van Alphen (dHvA) effect in BaFe_2P_2 which is the end member of the superconducting series, BaFe_2(As_{1-x}P_x)_2. Using high purity samples we are able to observe dHvA oscillations from all the sheets of ... More
Atmospheric neutrino flux calculation using the NRLMSISE00 atmospheric modelFeb 13 2015May 26 2015In this paper, we extend the calculation of the atmospheric neutrino flux~\cite{hkkm2004,hkkms2006,hkkm2011} to the sites in polar and tropical regions. In our earliest full 3D-calculation~\cite{hkkm2004}, we used DPMJET-III~\cite{dpm} for the hadronic ... More
Atmospheric neutrino flux at INO, South Pole and PyhäsalmiOct 18 2012We present the calculation of the atmospheric neutrino fluxes for the neutrino experiments proposed at INO, South Pole and Pyh\"asalmi. Neutrino fluxes have been obtained using ATMNC, a simulation code for cosmic ray in the atmosphere. Even using the ... More
Evidence for the Presence of Spin Accumulation in Localized States at Ferromagnet-Silicon InterfacesJul 05 2012We experimentally show evidence for the presence of spin accumulation in localized states at ferromagnet-silicon interfaces, detected by electrical Hanle effect measurements in CoFe/$n^{+}$-Si/$n$-Si lateral devices. By controlling the measurement temperature, ... More
Coupling between heavy fermion superconductor CeCoIn$_5$ and antiferromagnetic metal CeIn$_3$ through the atomic interfaceApr 15 2019To study the mutual interaction between unconventional superconductivity and magnetic order through an interface, we fabricate Kondo superlattices consisting of alternating layers of heavy-fermion superconductor CeCoIn$_5$ and antiferromagnetic (AFM) ... More
Effect of the magnetic domain structure in the ferromagnetic contact on spin accumulation in siliconOct 02 2012We show a marked effect of the magnetic domain structure in an epitaxial CoFe contact on the spin accumulation signals in Si detected by three-terminal Hanle-effect measurements. Clear reduction in the spin accumulation signals can be seen by introducing ... More
Feasibility study of probing the high energy end of the primary cosmic electron spectrum by detecting geo-synchrotron X-raysApr 13 2011Based on tests of a tentative detector for observing geo-synchrotron hard X-rays generated by primary electrons, we study the feasibility of probing cosmic electrons above a few TeV to over 10 TeV. Such high energy electrons are expected to give proof ... More
Nematic quantum critical point without magnetism in FeSe1-xSx superconductorsApr 01 2016Apr 04 2016The importance of antiferromagnetic fluctuations are widely acknowledged in most unconventional superconductors. In addition, cuprates and iron pnictides often exhibit unidirectional (nematic) electronic correlations, including stripe and orbital orders, ... More
Normal state spin dynamics in the iron-pnictide superconductors BaFe2(As1-xPx)2 and Ba(Fe1-xCox)2As2 probed with NMR measurementsMay 13 2013The NMR results in iron pnictides BaFe2(As1-xPx)2 and Ba(Fe1-xCox)2As2 are analyzed based on the self-consistent renormalization (SCR) spin fluctuation theory. The temperature dependence of the NMR relaxation rate (T_1)^{-1} as well as the electrical ... More
Unconventional superconductivity and antiferromagnetic quantum critical behavior in the isovalent-doped BaFe2(As1-xPx)2May 17 2010Sep 03 2010Spin dynamics evolution of BaFe$_2$(As$_{1-x}$P$_x$)$_2$ was probed as a function of P concentration via $^{31}$P NMR. Our NMR study reveals that two-dimensional antiferromagnetic (AF) fluctuations are notably enhanced with little change in static susceptibility ... More
Optical Conductivity Evidence of Clean-Limit Superconductivity in LiFeAsApr 26 2015We measured the optical conductivity of superconducting LiFeAs. In the superconducting state, the formation of the condensate leads to a spectral-weight loss and yields a penetration depth of 225 nm. No sharp signature of the superconducting gap is observed. ... More
Specific Heat vs Field in the 30 K Superconductor BaFe2(As0.7P0.3)2Feb 17 2010May 20 2010We report specific heat measurements on the Fe-based superconductor BaFe2(As0.7P0.3)2, a material on which previous penetration depth, NMR, and thermal conductivity measurements have observed a high density of low-energy excitations, which have been interpreted ... More
Test by JANZOS of the Standard Model of Cosmic Ray Acceleration in the COMPTEL/ROSAT Supernova RenmantNov 22 1999A search for ultra-high energy gamma-rays emitted by the young, nearby supernova remnant that was discovered recently by the COMPTEL and ROSAT satellites was made using the JANZOS database for the period 1987-1993. A 95% confidence upper limit on the ... More
Priority Mechanism of Bitcoin and Its Effect on Transaction-Confirmation ProcessApr 01 2016Apr 04 2016In Bitcoin system, transactions are prioritized according to attributes such as the remittance amount and transaction fees, and transactions with low priority are likely to wait for confirmation. Because the demand of micro payment in Bitcoin is expected ... More
Isostaticity and Mechanical Response of Two-Dimensional Granular PilesMay 08 2004We numerically study the static structure and the mechanical response of two-dimensional granular piles. The piles consist of polydisperse disks with and without friction. Special attention is paid for the rigid grain limit by examining the systems with ... More
A uniqueness of periodic maps on surfacesNov 28 2014Feb 10 2015Kulkarni showed that, if g is greater than 3, a periodic map on an oriented surface S_g of genus g with order more than or equal to 4g is uniquely determined by its order, up to conjugation and power. In this paper, we show that, if g is greater than ... More
Effect of Bitcoin fee on transaction-confirmation processApr 01 2016May 30 2017In Bitcoin system, transactions are prioritized according to transaction fees. Transactions without fees are given low priority and likely to wait for confirmation. Because the demand of micro payment in Bitcoin is expected to increase due to low remittance ... More
Asymptotic Properties of the Maximum Likelihood Estimator in Regime Switching Econometric ModelsMay 30 2017Jun 28 2018Markov regime switching models have been widely used in numerous empirical applications in economics and finance. However, the asymptotic distribution of the maximum likelihood estimator (MLE) has not been proven for some empirically popular Markov regime ... More
Diamagnetic Vortex Barrier Stripes in Underdoped $BaFe_2(As_{1-x}P_x)_2$Oct 29 2015May 31 2016We report magnetic force microscopy (MFM) measurements on underdoped $BaFe_2(As_{1-x}P_x)_2$ ($x=0.26$) that show enhanced superconductivity along stripes parallel to twin boundaries. These stripes of enhanced diamagnetic response repel vortices when ... More
Emergent exotic superconductivity in artificially-engineered tricolor Kondo superlatticesNov 17 2017In the quest for exotic superconducting pairing states, the Rashba effect, which lifts the electron-spin degeneracy as a consequence of strong spin-orbit interaction (SOI) under broken inversion symmetry, has attracted considerable interest. Here, to ... More
Isostaticity in two dimensional pile of rigid disksDec 23 2003We study the static structure of piles made of polydisperse disks in the rigid limit with and without friction using molecular dynamic simulations for various elasticities of the disks and pile preparation procedures. The coordination numbers are calculated ... More
Testing the Number of Regimes in Markov Regime Switching ModelsJan 21 2018Jan 30 2018Markov regime switching models have been used in numerous empirical studies in economics and finance. However, the asymptotic distribution of the likelihood ratio test statistic for testing the number of regimes in Markov regime switching models has been ... More
Explicit representation of finite predictor coefficients and its applicationsMay 04 2004Jul 03 2006We consider the finite-past predictor coefficients of stationary time series, and establish an explicit representation for them, in terms of the MA and AR coefficients. The proof is based on the alternate applications of projection operators associated ... More
Nodeless vs nodal order parameters in LiFeAs and LiFeP superconductorsJul 22 2011High-precision measurements of magnetic penetration depth $\lambda$ in clean single crystals of LiFeAs and LiFeP superconductors reveal contrasting low-energy quasiparticle excitations. In LiFeAs the low-temperature $\lambda(T)$ shows a flat dependence ... More
Anisotropic order parameter in Li-intercalated layered superconductor Li$_x$ZrNClOct 29 2009Jan 21 2010In this study, it is shown that in a layered nitride superconductor, i.e., LixZrNCl (0.07<=x<=0.21), the superconducting order parameter is highly anisotropic in a sample with x=0.12, as inferred from both the temperature and the magnetic field dependences ... More
Anisotropic Superconducting Properties of Optimally Doped BaFe$_2$(As$_{0.65}$P$_{0.35}$)$_2$ under PressureJun 30 2010Sep 02 2010Magnetic measurements on optimally doped single crystals of BaFe$_2$(As$_{1-x}$P$_{x}$)$_2$ ($x\approx0.35$) with magnetic fields applied along different crystallographic axes were performed under pressure, enabling the pressure evolution of coherence ... More
Spin accumulation created electrically in an n-type germanium channel using Schottky tunnel contactsMay 05 2011Oct 18 2011Using high-quality Fe$_{3}$Si/$n^{+}$-Ge Schottky-tunnel-barrier contacts, we study spin accumulation in an $n$-type germanium ($n$-Ge) channel. In the three- or two-terminal voltage measurements with low bias current conditions at 50 K, Hanle-effect ... More
Testing the Order of Multivariate Normal Mixture ModelsFeb 08 2019Finite mixtures of multivariate normal distributions have been widely used in empirical applications in diverse fields such as statistical genetics and statistical finance. Testing the number of components in multivariate normal mixture models is a long-standing ... More
Identification of Regression Models with a Misclassified and Endogenous Binary RegressorApr 25 2019We study identification in nonparametric regression models with a misclassified and endogenous binary regressor when an instrument is correlated with misclassification error. We show that the regression function is nonparametrically identified if one ... More
Temperature evolution of spin accumulation detected electrically in a nondegenerated silicon channelJan 28 2012We study temperature evolution of spin accumulation signals obtained by the three-terminal Hanle effect measurements in a nondegenerated silicon channel with a Schottky-tunnel-barrier contact. We find the clear difference in the temperature-dependent ... More
Diagonal Nematicity in the Pseudogap Phase of HgBa$_2$CuO$_{4+δ}$May 01 2018The pseudogap phenomenon in cuprates is the most mysterious puzzle in the research of high-temperature superconductivity. In particular, whether the pseudogap is associated with a crossover or phase transition has been a long-standing controversial issue. ... More
Volovik effect in a highly anisotropic multiband superconductor: experiment and theorySep 02 2011We present measurements of the specific heat coefficient \gamma(= C/T) in the low temperature limit as a function of an applied magnetic field for the Fe-based superconductor BaFe$_2$(As$_{0.7}$P$_{0.3}$)$_2$. We find both a linear regime at higher fields ... More
Coexistence of orbital and quantum critical magnetoresistance in FeSe$_{1-x}$S$_{x}$Mar 13 2019The recent discovery of a non-magnetic nematic quantum critical point (QCP) in the iron chalcogenide family FeSe$_{1-x}$S$_{x}$ has raised the prospect of investigating, in isolation, the role of nematicity on the electronic properties of correlated metals. ... More
Spin nematic susceptibility studied by inelastic neutron scattering in FeSeNov 13 2015Sep 22 2016Mechanism of unconventional superconductivity in FeSe has been intensely scrutinized recently because of a variety of exotic properties unprecedented for other iron-based superconductors. A central unanswered question concerns the origin of the interaction ... More
Nematic and meta-nematic transitions in the iron pnictidesJul 04 2012Strongly interacting electrons can exhibit novel collective phases, among which the electronic nematic phases are perhaps the most surprising as they spontaneously break rotational symmetry of the underlying crystal lattice. The electron nematicity has ... More
Evolution from Non-Fermi to Fermi Liquid Transport Properties by Isovalent Doping in BaFe2(As1-xPx)2 SuperconductorsMay 27 2009Feb 09 2010The normal-state charge transport is studied systematically in high-quality single crystals of BaFe$_2$(As$_{1-x}$P$_x$)$_2$ ($0 \leq x \leq 0.71$). By substituting isovalent P for As, the spin-density-wave (SDW) state is suppressed and the dome-shaped ... More
Disorder-induced topological change of the superconducting gap structure in iron pnictidesMay 27 2014May 29 2014In superconductors with unconventional pairing mechanisms, the energy gap in the excitation spectrum often has nodes, which allow quasiparticle excitations at low energies. In many cases, e.g. $d$-wave cuprate superconductors, the position and topology ... More
Charge induced nematicity in FeSeMar 04 2016Aug 19 2016The spontaneous appearance of nematicity, a state of matter that breaks rotation but not translation symmetry, is one of the most intriguing property of the iron based superconductors (Fe SC), and has relevance for the cuprates as well. Establishing the ... More
Line nodes in the energy gap of high-temperature superconducting BaFe_2(As_{1-x}P_x)_2 from penetration depth and thermal conductivity measurementsJul 25 2009May 17 2010We report magnetic penetration depth and thermal conductivity data for high-quality single crystals of BaFe$_2$(As$_{1-x}$P$_{x}$)$_2$ ($T_c=30$\,K) which provide strong evidence that this material has line nodes in its energy gap. This is distinctly ... More
Quadrupole Order in the Frustrated Pyrochlore Tb$_{2+x}$Ti$_{2-x}$O$_{7+y}$Jun 15 2015Apr 17 2016A hidden order that emerges in the frustrated pyrochlore Tb$_{2+x}$Ti$_{2-x}$O$_{7+y}$ with $T_{\text{c}}=0.53$ K is studied using specific heat, magnetization, and neutron scattering experiments on a high-quality single crystal. Semi-quantitative analyses ... More
Two- and Three-Dimensional Fermi Surfaces and their Nesting Properties in Superconducting BaFe2(As1-xPx)2Aug 12 2010We have studied the three-dimensional shapes of the Fermi surfaces (FSs) of BaFe2(As1-xPx)2 (x=0.38), where superconductivity is induced by isovalent P substitution, by angle-resolved photoemission spectroscopy. Moderately strong electron mass enhancement ... More
Structural origin of the anomalous temperature dependence of the local magnetic moments in the CaFe$_{2}$As$_{2}$ family of materialsAug 18 2014We report a combination of Fe K$\beta$ x-ray emission spectroscopy and $ab$-intio calculations to investigate the correlation between structural and magnetic degrees of freedom in CaFe$_{2}$(As$_{1-x}$P$_{x} $)$_{2}$. The puzzling temperature behavior ... More
Tuning the pairing interaction in a $d$-wave superconductor by paramagnons injected through interfacesDec 01 2017Unconventional superconductivity and magnetism are intertwined on a microscopic level in a wide class of materials. A new approach to this most fundamental and hotly debated issue focuses on the role of interactions between superconducting electrons and ... More
Nodal gap structure of BaFe_2(As_{1-x}P_x)_2 from angle-resolved thermal conductivity in a magnetic fieldMar 04 2011Aug 25 2011The structure of the superconducting order parameter in the iron-pnictide superconductor BaFe$_2$(As$_{0.67}$P$_{0.33}$)$_2$ ($T_c=31$\,K) with line nodes is studied by the angle-resolved thermal conductivity measurements in a magnetic field rotated within ... More
Evidence for time-reversal symmetry breaking of the superconducting state near twin-boundary interfaces in FeSeApr 09 2015Junctions and interfaces consisting of unconventional superconductors provide an excellent experimental playground to study exotic phenomena related to the phase of the order parameter. Not only the complex structure of unconventional order parameters ... More
Full-gap superconductivity robust against disorder in heavy-fermion CeCu2Si2May 17 2017Jul 28 2017A key aspect of unconventional pairing by the antiferromagnetic spin-fluctuation mechanism is that the superconducting energy gap must have opposite sign on different parts of the Fermi surface. Recent observations of non-nodal gap structure in the heavy-fermion ... More
Quantum sensing of local magnetic field texture in strongly correlated electron systems under extreme conditionsDec 25 2018An important feature of strong correlated electron systems is the tunability between interesting ground states such as unconventional superconductivity and exotic magnetism. Pressure is a clean, continuous and systematic tuning parameter. However, due ... More
Letter of intent; Precise measurements of very forward particle production at RHICJan 06 2014In this paper, we propose an experiment for the precise measurements of very forward particle production at RHIC. The proposal is to install a LHCf-like calorimeter in the ZDC installation slot at one of the RHIC interaction points. By installing a high-resolution ... More
Electric-field control of spin accumulation signals in silicon at room temperatureAug 24 2011We demonstrate spin-accumulation signals controlled by the gate voltage in a metal-oxide-semiconductor field effect transistor structure with a Si channel and a CoFe/$n^{+}$-Si contact at room temperature. Under the application of a back-gate voltage, ... More
Discovery of Emergent Photon and Monopoles in a Quantum Spin LiquidMar 15 2018Quantum spin liquid (QSL) is an exotic quantum phase of matter whose ground state is quantum-mechanically entangled without any magnetic ordering. A central issue concerns emergent excitations that characterize QSLs, which are hypothetically associated ... More
Weakening of the diamagnetic shielding in FeSe$_{1-x}$S$_x$ at high pressuresMay 22 2017Jul 10 2017The superconducting transition of FeSe$_{1-x}$S$_x$ with three distinct sulphur concentrations $x$ was studied under hydrostatic pressure up to $\sim$70 kbar via bulk AC susceptibility. The pressure dependence of the superconducting transition temperature ... More
Evolution of the Fermi surface of the nematic superconductors FeSe1-xSxNov 22 2016We investigate the evolution of the Fermi surfaces and electronic interactions across the nematic phase transition in single crystals of FeSe1-xSx using Shubnikov-de Haas oscillations in high magnetic fields up to 45 tesla in the low temperature regime. ... More
Model predictive control for energy-efficient operation of data centers with cold aisle containmentsJun 08 2018In this paper, we study a problem of controlling cooling facilities and computational equipments for energy-efficient operations of data centers. Although a plethora of approaches have been proposed in previous literatures, there is a lack of rigorous ... More
Baxter's inequality for finite predictor coefficients of multivariate long-memory stationary processesJul 10 2015Sep 02 2016For a multivariate stationary process, we develop explicit representations for the finite predictor coefficient matrices, the finite prediction error covariance matrices and the partial autocorrelation function (PACF) in terms of the Fourier coefficients ... More
Fully gapped superconductivity with no sign change in the prototypical heavy-fermion CeCu2Si2Mar 08 2017In exotic superconductors including high-$T_c$ copper-oxides, the interactions mediating electron Cooper-pairing are widely considered to have a magnetic rather than the conventional electron-phonon origin. Interest in such exotic pairing was initiated ... More
Superconducting gap with sign reversal between hole pockets in heavily hole-doped Ba1-xKxFe2As2Jul 12 2013To gain insight into the unconventional superconductivity of Fe-pnictides with no electron pockets, we measure the thermal conductivity $\kappa$ and penetration depth $\lambda$ in the heavily hole-doped regime of Ba$_{1-x}$K$_x$Fe$_2$As$_2$. The residual ... More
Infrared Measurement of the Pseudogap in P-Doped and Co-Doped BaFe2As2 High-Temperature SuperconductorsJul 16 2012We report on infrared studies of charge dynamics in a prototypical pnictide system: the BaFe2As2 family. Our experiments have identified hallmarks of the pseudogap state in the BaFe2As2 system that mirror the spectroscopic manifestations of the pseudogap ... More
Magneto-elastic coupling in Fe-based superconductorsDec 05 2017We used polarization-resolved Raman scattering to study the magneto-elastic coupling in the parent compounds of several families of Fe-based superconductors (BaFe2As2, EuFe2As2, NaFeAs, LiFeAs, FeSe and LaFeAsO). We observe an emergent Ag-symmetry As ... More
Dark Matter in the MSSM Golden RegionMay 07 2008Dark matter is examined within the ``golden region'' of the Minimal Supersymmetric Standard Model. This region satisfies experimental constraints, including a lower bound on the Higgs mass of 114 GeV, and minimizes fine-tuning of the Z boson mass. Here ... More
Disorder, critical currents, and vortex pinning energies in isovalently substituted BaFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$Mar 14 2013We present a comprehensive overview of vortex pinning in single crystals of the isovalently substituted iron-based superconductor BaFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$, a material that qualifies as an archetypical clean superconductor, containing only sparse ... More
Enumerating Graph Partitions Without Too Small Connected Components Using Zero-suppressed Binary and Ternary Decision DiagramsApr 06 2018Partitioning a graph into balanced components is important for several applications. For multi-objective problems, it is useful not only to find one solution but also to enumerate all the solutions with good values of objectives. However, there are a ... More
Applications of a finite-dimensional duality principle to some prediction problemsAug 29 2007Some of the most important results in prediction theory and time series analysis when finitely many values are removed from or added to its infinite past have been obtained using difficult and diverse techniques ranging from duality in Hilbert spaces ... More
Baxter's inequality for fractional Brownian motion-type processes with Hurst index less than 1/2Jan 16 2008The aim of this paper is to prove an analogue of Baxter's inequality for fractional Brownian motion-type processes with Hurst index less than 1/2. This inequality is concerned with the norm estimate of the difference between finite- and infinite-past ... More
An explicit representation of Verblunsky coefficientsSep 21 2011We prove a representation of the partial autocorrelation function (PACF) of a stationary process, or of the Verblunsky coefficients of its normalized spectral measure, in terms of the Fourier coefficients of the phase function. It is not of fractional ... More
Anomalous critical fields in quantum critical superconductorsFeb 06 2014Dec 15 2014Fluctuations around an antiferromagnetic quantum critical point (QCP) are believed to lead to unconventional superconductivity and in some cases to high-temperature superconductivity. However, the exact mechanism by which this occurs remains poorly understood. ... More