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Results for "M. Gu"

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New Benchmark of X-ray Line Emission Models of Fe XVIIMay 05 2009We review the accuracy of existing \ion{Fe}{17} X-ray line emission models by comparing them with an extensive analysis of \textit{Chandra} high energy transmission grating (HETG) observations of stellar coronae. We find significant discrepancies between ... More
Connectivity, toughness, spanning trees of bounded degree, and the spectrum of regular graphsFeb 18 2016In this paper, we present some new results describing connections between the spectrum of a regular graph and its generalized connectivity, toughness, and the existence of spanning trees with bounded degree.
Collapsing and Separating Completeness Notions under Average-Case and Worst-Case HypothesesJan 04 2010Feb 03 2010This paper presents the following results on sets that are complete for NP. 1. If there is a problem in NP that requires exponential time at almost all lengths, then every many-one NP-complete set is complete under length-increasing reductions that are ... More
Scaling Study of the Metal-Insulator Transition in one-Dimensional Fermion SystemsMar 20 2003We consider the Ising phase of the antiferromagnetic XXZ Heisenberg chain on a finite-size lattice with N sites.We compute the large $N$ behavior of the spin stiffness, obtaining the correlation length \xi. We use our results to discuss the scaling behavior ... More
Spin Susceptibility in Underdoped Cuprates: Insights from a Stripe-Ordered CrystalMar 17 2005Nov 10 2008We report a detailed study of the temperature and magnetic-field dependence of the spin susceptibility for a single crystal of La(1.875)Ba(0.125)CuO(4). From a quantitative analysis, we find that the temperature-dependent anisotropy of the susceptibility, ... More
A reduced complexity numerical method for optimal gate synthesisNov 28 2010Although quantum computers have the potential to efficiently solve certain problems considered difficult by known classical approaches, the design of a quantum circuit remains computationally difficult. It is known that the optimal gate design problem ... More
Inner-shell Absorption Lines of Fe~VI-- Fe~XVI: A Many-body Perturbation Theory ApproachDec 15 2005We provide improved atomic calculation of wavelengths, oscillator strengths, and autoionization rates relevant to the $2\to 3$ inner-shell transitions of Fe~VI--XVI, the so-called Fe~M-shell unresolved transition array (UTA). A second order many-body ... More
vdW-corrected density functional study of electric field noise heating in ion traps caused by electrode surface adsorbatesOct 24 2018In order to realize the full potential of ion trap quantum computers, an improved understanding is required of the motional heating that trapped ions experience. Experimental studies of the temperature-, frequency-, and ion-electrode distance-dependence ... More
Robust charge and magnetic order under electric field and current in the multiferroic LuFe(2)O(4)Jan 20 2010Apr 20 2010We performed elastic neutron scattering measurements on the charge- and magnetically-ordered multiferroic material LuFe(2)O(4). An external electric field along the [001] direction with strength up to 20 kV/cm applied at low temperature (~100 K) does ... More
SymFET: A Proposed Symmetric Graphene Tunneling Field Effect TransistorJan 04 2013In this work, an analytical model to calculate the channel potential and current-voltage characteristics in a Symmetric tunneling Field-Effect-Transistor (SymFET) is presented. The current in a SymFET flows by tunneling from an n-type graphene layer to ... More
Spontaneous symmetry breaking by charge stripes in the high-pressure phase of superconducting La(1.875)Ba(0.125)CuO(4)Sep 29 2009Feb 03 2010In those cases where charge stripe order has been observed in cuprates, the crystal structure is such that the average rotational symmetry of the CuO2 planes is reduced from four-fold to two-fold. As a result, one could argue that the reduced lattice ... More
On a measure of distance for quantum strategiesAug 27 2010Mar 14 2012The present paper studies an operator norm that captures the distinguishability of quantum strategies in the same sense that the trace norm captures the distinguishability of quantum states or the diamond norm captures the distinguishability of quantum ... More
Spanning rigid subgraph packing and sparse subgraph coveringMay 01 2014Jun 12 2018Rigidity, arising in discrete geometry, is the property of a structure that does not flex. Laman provides a combinatorial characterization of rigid graphs in the Euclidean plane, and thus rigid graphs in the Euclidean plane have applications in graph ... More
Some Torsion Classes in the Chow ring and Cohomology of $BPGL_n$Jan 29 2019In the integral cohomology ring of the classifying space of the projective linear group $PGL_n$ (over $\mathbb{C}$), we find a collection of $p$-torsions $y_{p,k}$ of degree $2(p^{k+1}+1)$ for any odd prime divisor $p$ of $n$, and $k\geq 0$. Similarly, ... More
Unconventional temperature enhanced magnetism in iron tellurideMar 25 2011Highly energetic magnetic fluctuations, discovered in high-temperature superconductors (HTSC) by inelastic neutron scattering (INS), are now widely believed to be vital for the superconductivity. In two competing scenarios, they either originate from ... More
High-energy magnetic excitations from dynamic stripes in LBCO (x=1/8)Feb 01 2007We use inelastic neutron scattering to study the temperature dependence of magnetic excitations (for energies up to 100 meV) in the cuprate La$_{1.875}$Ba$_{0.125}$CuO$_4$. This compound exhibits stripe order below a temperature of ~50 K; previous measurements ... More
Peak Effect of Flux Pinning in Sc5Ir4Si10 SuperconductorsOct 15 2010Magnetic hysteresis loops (MHLs) have been comparatively measured on both textured and single crystalline Sc5Ir4Si10 superconductors. Critical current densities and flux pinning forces are calculated from MHLs by Bean model. Three kinds of peaks of the ... More
On Pluri-canonical Systems of Arithmetic SurfacesSep 01 2014Let $S$ be a Dedekind scheme with perfect residue fields at closed points, let $f: X\rightarrow S$ be a minimal regular arithmetic surface of fibre genus at least $2$ and let $f': X'\rightarrow S$ be the canonical model of $f$. It is well known that $\omega_{X'/S}$ ... More
A strongly inhomogeneous superfluid in an iron-based superconductorJan 01 2019Among the mysteries surrounding unconventional, strongly correlated superconductors is the possibility of spatial variations in their superfluid density. We use atomic-resolution Josephson scanning tunneling microscopy to reveal a strongly inhomogeneous ... More
Quantum Strategies and Local OperationsFeb 26 2010Mar 14 2012This thesis is divided into two parts. In Part I we introduce a new formalism for quantum strategies, which specify the actions of one party in any multi-party interaction involving the exchange of multiple quantum messages among the parties. This formalism ... More
Short Quantum GamesNov 03 2005In this thesis we introduce quantum refereed games, which are quantum interactive proof systems with two competing provers. We focus on a restriction of this model that we call "short quantum games" and we prove an upper bound and a lower bound on the ... More
A partition of connected graphsMay 09 2005We define an algorithm k which takes a connected graph G on a totally ordered vertex set and returns an increasing tree R (which is not necessarily a subtree of G). We characterize the set of graphs G such that k(G)=R. Because this set has a simple structure ... More
On the Cohomology of the Classifying Spaces of Projective Unitary GroupsDec 01 2016Jan 29 2019Let $\mathbf{B}PU_{n}$ be the classifying space of $PU_n$, the projective unitary group of order $n$, for $n>1$. We use the Serre spectral sequence associated to a fiber sequence $\mathbf{B}U_n\rightarrow\mathbf{B}PU_n\rightarrow K(\mathbb{Z},3)$ to determine ... More
A remark on descent for Coxeter groupsJul 04 2017Jul 06 2017Let $\Gamma$ be a finite Coxeter group with reflection representation $R$. We show that a $\Gamma$-equivariant quasicoherent sheaf on $R$ descends to the quotient space $R//\Gamma$ if it descends to the quotient space $R//\langle s_i\rangle$ for every ... More
The Topological Period-Index Problem over 8-ComplexesSep 04 2017We study the Postnikov tower of the classifying space of a compact Lie group P(n,mn), which gives obstructions to lifting a topological Brauer class of period $n$ to a PU_{mn}-torsor, where the base space is a CW complex of dimension 8. Combined with ... More
Integrable systems from the classical reflection equationMay 21 2014Jun 08 2015We construct integrable Hamiltonian systems on $G/K$, where $G$ is a quasitriangular Poisson Lie group and $K$ is a Lie subgroup arising as the fixed point set of a group automorphism $\sigma$ of $G$ satisfying the classical reflection equation. In the ... More
The evolution of dusty torus covering factor in quasarsJul 04 2013Jul 15 2013We have assembled a large sample of 5996 quasars at redshift 2.0=< z <= 2.4 (high-z) or 0.7=< z <= 1.1 (low-z) from SDSS data release nine and seven quasar catalogs. The spectral energy distribution (SED) of quasars were constructed by collecting WISE, ... More
Surface effect on the wrinkling of an elastic sheet under tensionOct 27 2013Nov 21 2013Wrinkling of stretched elastic sheets is widely observed, and the scaling relations between the amplitude and wavelength of the wrinkles have been proposed by Cerda and Mahadevan. However, the surface effects should be taken into account when the sheet ... More
Uniform estimate of an iterative method for elliptic problems with rapidly oscillating coefficientsJul 17 2018Jan 07 2019We study the iterative algorithm proposed by S. Armstrong, A. Hannukainen, T. Kuusi, J.-C. Mourrat to solve elliptic equations in divergence form with stochastic stationary coefficients. Such equations display rapidly oscillating coefficients and thus ... More
Set maps, umbral calculus, and the chromatic polynomialJul 03 2005Jul 05 2007Some important properties of the chromatic polynomial also hold for any polynomial set map satisfying p_S(x+y)=\sum_{T\uplus U=S}p_T(x)p_U(y). Using umbral calculus, we give a formula for the expansion of such a set map in terms of any polynomial sequence ... More
On Topological Brauer Classes over $8$-Complexes with Periods Divisible by $4$Mar 14 2018We determine the index of the topological Brauer class $\beta_n$, the canonical generator of $H^3(X;\mathbb{Z})$, where $X$ is the $8$th skeleton of the Eilenberg-Mac Lane space $K(\mathbb{Z}/n,2)$, and $4|n$. This makes an important complement to a theorem ... More
Regularity criteria for suitable weak solutions to the four dimensional incompressible magneto-hydrodynamic equations near boundaryMay 19 2014In this paper, we consider suitable weak solutions of the four dimensional incompressible magneto-hydrodynamic equations. We give two different kind $\varepsilon$-regularity criteria. One only requires the smallness of scaling $L^{p,q}$ norm of $u$, another ... More
A Study of Weakly Discontinuous Solutions for Hyperbolic Differential Equations Based on Wavelet Transform MethodsNov 03 2013Dec 04 2013A new approach to prove the one-dimensional Cauchy problem's weakly discontinuous solutions for hyperbolic PDEs are on the characteristics is discussed in this paper. To do so, I use wavelet singularity detection methods or WTMM [1] based on two-dimensional ... More
On algebraic surfaces of general type with negative c2Nov 30 2014Dec 08 2014We prove that for any prime number $p\ge 3$, there exists a positive number $\kappa_p$ such that $\chi(\mathcal{O}_X)\ge \kappa_pc_1^2$ holds true for all algebraic surfaces $X$ of general type in characteristic $p$. In particular, $\chi(\mathcal{O}_X)>0$. ... More
Quantum Action Principle with Generalized Uncertainty PrincipleNov 01 2013One of the common features in all promising candidates of quantum gravity is the existence of a minimal length scale, which naturally emerges with a generalized uncertainty principle, or equivalently a modified commutation relation. Schwinger's quantum ... More
Reconstruction-Stabilized Epitaxy of LaCoO3/SrTiO3(111) Heterostructures by Pulsed Laser DepositionJan 04 2018Unlike widely explored complex oxide heterostructures grown along [001], the study of [111]-oriented heterointerfaces are very limited thus far. One of the main challenges is to overcome the polar discontinuity that hinders the epitaxy of atomically sharp ... More
The Hard X-ray emission of the blazar PKS 2155--304Oct 23 2017The synchrotron peak of the X-ray bright High Energy Peaked Blazar (HBL) PKS 2155$-$304 occurs in the UV-EUV region and hence its X-ray emission (0.6--10 keV) lies mostly in the falling part of the synchrotron hump. We aim to study the X-ray emission ... More
Interplay between magnetism and superconductivity in iron-chalcogenide superconductors: crystal growth and characterizationsApr 04 2011Jul 09 2011In this review, we present a summary of the results on single crystal growth of two types of iron-chalcogenide superconductors, Fe(1+y)Te(1-x)Se(x) (11), and A(x)Fe(2-y)Se(2) (A= K, Rb, Cs, Tl, Tl/K, Tl/Rb), using Bridgman, zone-melting, vapor self-transport, ... More
Evidence of Chiral Order in the Charge-Ordered Phase of Superconducting La1.875Ba0.125Cuo4 Single Crystals Using Polar Kerr-Effect MeasurementsAug 22 2013Feb 25 2014High resolution polar Kerr effect (PKE) measurements were performed on La1.875Ba0.125Cuo4 single crystals revealing that a finite Kerr signal is measured below an onset temperature-T_K that coincides with charge ordering transition temperature T_{CO}. ... More
Magneto-optical signatures of a cascade of transitions in La$_2-x$Ba$_x$CuO$_4$Mar 13 2012Jul 19 2012Recent experiments in the original cuprate high temperature superconductor, La$_2-x$Ba$_x$CuO$_4$, have revealed a remarkable sequence of transitions [1]. Here we investigate such crystals with Kerr effect which is sensitive to time-reversal-symmetry ... More
Combined single crystal polarized XAFS and XRD at high pressure: probing the interplay between lattice distortions and electronic order at multiple length scales in high $T_c$ cupratesJun 07 2016Some of the most exotic material properties derive from electronic states with short correlation length (~10-500 {\AA}), suggesting that the local structural symmetry may play a relevant role in their behavior. Here we discuss the combined use of polarized ... More
Neutrino masses, leptogenesis and dark matter in hybrid seesawNov 06 2008We suggest a hybrid seesaw model where relatively ``light''right-handed neutrinos give no contribution to the neutrino mass matrix due to a special symmetry. This allows their Yukawa couplings to the standard model particles to be relatively strong, so ... More
Operational resource theory of continuous-variable nonclassicalityApr 26 2018Dec 10 2018Genuinely quantum states of a harmonic oscillator may be distinguished from their classical counterparts by the Glauber-Sudarshan P-representation -- a state lacking a positive P-function is said to be nonclassical. In this paper, we propose a general ... More
Baryon content and dynamic state of galaxy clusters: XMM-Newton observations of A1095 and A1926Mar 11 2016We have initiated a program to study the baryon content and dynamic state of galaxy clusters. Here we present results primarily from XMM-Newton observations of two optically-selected galaxy clusters, A1095 ($z \simeq 0.210$) and A1926 ($z \simeq 0.136$). ... More
Magnetic field control of charge structures in the magnetically disordered phase of the multiferroic LuFe$_2$O$_4$Apr 09 2009Apr 10 2009Using neutron diffraction, we have studied the magnetic field effect on charge structures in the charge-ordered multiferroic material LuFe$_2$O$_4$. An external magnetic field is able to change the magnitude and correlation lengths of the charge valence ... More
Field-enhanced diamagnetism in intense magnetic field in the pseudogap state of the cuprate $\rm Bi_2Sr_2CaCu_2O_{8+δ}Mar 08 2005Oct 20 2005In hole-doped cuprates, Nernst experiments imply that the superconducting state is destroyed by spontaneous creation of vortices which destroy phase coherence. Using torque magnetometry on $\rm Bi_2Sr_2CaCu_2O_{8+\delta}$, we uncover a field-enhanced ... More
Generalized isobaric multiplet mass equation and its application to the Nolen-Schiffer anomalyDec 25 2017Feb 02 2018The Wigner Isobaric Multiplet Mass Equation (IMME) is the most fundamental prediction in nuclear physics with the concept of isospin. However, it was deduced based on the Wigner-Eckart theorem with the assumption that all charge-violating interactions ... More
Overarching framework between Gaussian quantum discord and Gaussian quantum illuminationNov 30 2016Feb 28 2017We cast the problem of illuminating an object in a noisy environment into a communication protocol. A probe is sent into the environment, and the presence or absence of the object constitutes a signal encoded on the probe. The probe is then measured to ... More
Antiferromagnetism and chiral d-wave superconductivity from an effective $t-J-D$ model for twisted bilayer grapheneJan 31 2019Starting from the strong-coupling limit of an extended Hubbard model, we develop a spin-fermion theory to study the insulating phase and pairing symmetry of the superconducting phase in twisted bilayer graphene. Assuming that the insulating phase is an ... More
On the apparent permeability of porous media in rarefied gas flowsApr 12 2017The apparent gas permeability of the porous medium is an important parameter in the prediction of unconventional gas production, which was first investigated systematically by Klinkenberg in 1941 and found to increase with the reciprocal mean gas pressure ... More
FeTe$_{0.55}$Se$_{0.45}$: a multiband superconductor in the clean and dirty limitFeb 26 2015Apr 09 2015The detailed optical properties of the multiband iron-chalcogenide superconductor FeTe$_{0.55}$Se$_{0.45}$ have been reexamined for a large number of temperatures above and below the critical temperature $T_c=14$ K for light polarized in the a-b planes. ... More
Intra-day variability of three Seyfert Galaxies measured with XMM-NewtonMar 12 2019We present and analyze the variability of three Seyfert galaxies on intra-day timescales. We have analyzed in a uniform manner the 38 longest ( $>30$ ks) observations made for NGC 4051, MCG$-06-30-15$ and NGC 4151 by XMM-Newton between 2000 and 2015. ... More
Magnetic field induced anisotropy of $^{139}\mathrm{La}$ spin-lattice relaxation rates in stripe ordered ${\mathrm{La}}_{1.875}{\mathrm{Ba}}_{0.125}{\mathrm{CuO}}_{4}$Oct 26 2015We report $^{139}$La nuclear magnetic resonance studies performed on a La$_{1.875}$Ba$_{0.125}$CuO$_4$ single crystal. The data show that the structural phase transitions (high-temperature tetragonal $\rightarrow$ low-temperature orthorhombic $\rightarrow$ ... More
Anisotropic scattering rate in Fe substituted Bi2212May 17 2015We measured the electronic structure of Fe substituted Bi2212 using Angle Resolved Photoemission Spectroscopy (ARPES). We find that the substitution does not change the momentum dependence of the superconducting gap but induces a very anisotropic enhancement ... More
Charge order, metallic behavior and superconductivity in La_{2-x}Ba_xCuO_4 with x=1/8Mar 28 2006The ab-plane optical properties of a cleaved single crystal of La_{2-x}Ba_xCuO_4 for x=1/8 (T_c ~ 2.4 K) have been measured over a wide frequency and temperature range. The low-frequency conductivity is Drude-like and shows a metallic response with decreasing ... More
Protostar L1455 IRS1: Rotating Disk Connecting to Filamentary NetworkDec 24 2015Jun 02 2016We conducted IRAM-30m C18O (2-1) and SMA 1.3mm continuum, 12CO (2-1), and C18O (2-1) observations toward the Class 0/I protostar L1455 IRS1 in Perseus. The IRAM results show L1455 IRS1 located in a dense core of 0.05 pc in size with a mass of 0.54M_sun, ... More
The Energy Landscape Underpinning Module Dynamics in the Human Brain ConnectomeSep 05 2016Human brain dynamics can be profitably viewed through the lens of statistical mechanics, where neurophysiological activity evolves around and between local attractors representing preferred mental states. Many physically-inspired models of these dynamics ... More
Enhanced charge stripe order of superconducting La(2-x)Ba(x)CuO(4) in a magnetic fieldDec 14 2012The effect of a magnetic field on the charge stripe order in La(2-x)Ba(x)CuO(4) has been studied by means of high energy (100 keV) x-ray diffraction for charge carrier concentrations ranging from strongly underdoped to optimally doped. We find that charge ... More
Kepler-411: a four-planet system with an active host starFeb 26 2019We present a detailed characterization of the Kepler-411 system (KOI 1781). This system was previously known to host two transiting planets: one with a period of 3 days ($R=2.4R_\oplus$; Kepler-411b) and one with a period of 7.8 days ($R=4.4R_\oplus$; ... More
Determination of the optical properties of La{2-x}Ba{x}CuO{4} for several dopings, including the anomalous x=1/8 phaseOct 10 2011Apr 11 2012The optical properties the high-temperature superconductor La{2-x}Ba{x}CuO{4} have been measured over a wide frequency and temperature range for light polarized in the a-b planes and along the c axis. Three different Ba concentrations have been examined, ... More
Large Bi-2212 single crystal growth by the floating-zone techniqueMay 29 2008Effects of the growth velocity on the crystal growth behavior of Bi_2Sr_2Ca_1Cu_2O_x (Bi-2212) have been studied by floating zone technique. The results show that a necessary condition for obtaining large single crystals along the c-axis is that the solid-liquid ... More
Gapless spin excitations in superconducting La$_{2-x}$Ca$_{1+x}$Cu$_{2}$O$_{6}$ with $T_c$ up to 55 KFeb 20 2019We report inelastic neutron scattering on single crystals of the bilayer cuprate family La$_{2-x}$Ca$_{1+x}$Cu$_{2}$O$_{6+\delta}$, including two crystals made superconducting (transitions at 45 and 55 K) by high-pressure annealing in an oxygen-containing ... More
Nano-engineering of electron correlation in oxide superlatticesMar 14 2019Oxide heterostructures and superlattices have attracted a great deal of attention in recent years owing to the rich exotic properties encountered at their interfaces. We focus on the potential of tunable correlated oxides by investigating the spectral ... More
Optical studies of charge dynamics in the optimally-doped Bi2212 and the non-superconducting cobaltate single crystalsApr 11 2001An analysis of the frequency-dependent scattering rate reveals signatures of the superconducting gap as well as the pseudogap in high-T_c cuprates. These features can be identified in the temperature-dependent spectral function W(omega), inverted from ... More
Quantitative Raman measurements of the evolution of the Cooper-pairs density with doping in Bi2Sr2CaCu2O8+d superconductorsJan 17 2009Sep 21 2009We report Raman measurements on Bi2Sr2CaCu2O8+d single crystals which allow us to quantitavely evaluate the doping dependence of the density of Cooper pairs in the superconducting state. We show that the drastic loss of Cooper pairs in the antinodal region ... More
Neutron scattering study on La1.9Ca1.1Cu2O6+delta and La1.85Sr0.15CaCu2O6+deltaAug 13 2004We present neutron scattering data on two single crystals of the high temperature superconductor La2-x(Ca,Sr)xCaCu2O6+delta. The Ca0.1-doped crystal exhibits a long-range antiferromagnetically ordered ground state. In contrast, the Sr0.15-doped crystal ... More
Quantum Magnetic Excitations from Stripes in Copper-Oxide SuperconductorsJan 30 2004Apr 09 2004In the copper-oxide parent compounds of the high-transition-temperature superconductors, the valence electrons are localized, one per copper site, due to strong intraatomic Coulomb repulsion. A symptom of the localization is antiferromagnetism, where ... More
Low-energy antiferromagnetic spin fluctuations limit the coherent superconducting gap in cupratesJun 27 2018Dec 13 2018Motivated by recent attention to a potential antiferromagnetic quantum critical point at $x_c\sim 0.19$, we have used inelastic neutron scattering to investigate the low-energy spin excitations in crystals of La$_{2-x}$Sr$_x$CuO$_4$ bracketing $x_c$. ... More
Tuning from failed superconductor to failed insulator with magnetic fieldOct 24 2018Do charge modulations compete with electron pairing in high-temperature copper-oxide superconductors? We investigated this question by suppressing superconductivity in a stripe-ordered cuprate compound at low temperature with high magnetic fields. With ... More
Testing the itinerancy of spin dynamics in superconducting Bi2212Feb 16 2009May 27 2009Much of what we know about the electronic states of high-temperature superconductors is due to photoemission and scanning tunneling spectroscopy studies of the compound Bi2212. The demonstration of well-defined quasiparticles in the superconducting state ... More
Optimization of Surface Registrations using Beltrami Holomorphic FlowMay 14 2010In shape analysis, finding an optimal 1-1 correspondence between surfaces within a large class of admissible bijective mappings is of great importance. Such process is called surface registration. The difficulty lies in the fact that the space of all ... More
Strong pinning in the hole-doped pnictide superconductor La$_{0.34}$Na$_{0.66}$Fe$_2$As$_2$Mar 10 2019We present magnetization studies as a function of time, temperature and magnetic field for $H$ $\parallel$ c-axis, in a hole-doped pnictide superconductor, La$_{0.34}$Na$_{0.66}$Fe$_2$As$_2$, with, $T_c$ $\approx$ 27 K. The obtained vortex phase-diagram ... More
Comparison of charge modulations in La$_{1.875}$Ba$_{0.125}$CuO$_4$ and YBa$_2$Cu$_3$O$_{6.6}$May 23 2013A charge modulation has recently been reported in (Y,Nd)Ba$_2$Cu$_3$O$_{6+x}$ [Ghiringhelli {\em et al.} Science 337, 821 (2013)]. Here we report Cu $L_3$ edge soft x-ray scattering studies comparing the lattice modulation associated with the charge modulation ... More
On exterior calculus and curvature in piecewise-flat manifoldsDec 05 2012Simplicial, piecewise-flat discretizations of manifolds provide a clear path towards curvature analysis on discrete geometries and for solutions of PDE's on manifolds of complex topologies. In this manuscript we review and expand on discrete exterior ... More
Low energy magnetic excitations from the Fe$_{1+y-z}$(Ni/Cu)$_{z}$Te$_{1-x}$Se$_{x}$ systemApr 04 2014We report neutron scattering measurements on low energy ($\hbar\omega \sim 5$~meV) magnetic excitations from a series of Fe$_{1+y-z}$(Ni/Cu)$_{z}$Te$_{1-x}$Se$_{x}$ samples which belong to the "11" Fe-chalcogenide family. Our results suggest a strong ... More
Electronic Raman Scattering in copper oxide Superconductors: Understanding the Phase DiagramMar 29 2011Apr 30 2011Electronic Raman scattering measurements have been performed on hole doped copper oxide superconductors as a function of temperature and doping level. In the superconducting state coherent Bogoliubov quasiparticles develop preferentially over the nodal ... More
Deeply Embedded Protostellar Population in the 20 km s-1 Cloud of the Central Molecular ZoneOct 16 2015We report the discovery of a population of deeply embedded protostellar candidates in the 20 km s$^{-1}$ cloud, one of the massive molecular clouds in the Central Molecular Zone (CMZ) of the Milky Way, using interferometric submillimeter continuum and ... More
Quantum oscillations and Dirac dispersion in the BaZnBi2 semimetal guaranteed by local Zn vacancy orderJan 23 2018Mar 27 2018We have synthesized single crystals of Dirac semimetal candidates AZnBi2 with A=Ba and Sr. In contrast to A=Sr, the Ba material displays a novel local Zn vacancy ordering, which makes the observation of quantum oscillations in out-of-plane magnetic fields ... More
The mid-infrared AC Hall effect in optimally-doped BSCCOOct 14 2002Nov 21 2002A novel heterodyne polarimetry system determines the frequency dependence from 900 to 1100 cm^-1 and temperature dependence from 35 to 330 K of the Hall transport in single crystal, optimally doped BSCCO. The results show a significant disconnect from ... More
Morphology of Graphene on SiC(000-1) SurfacesJul 30 2009Aug 13 2009Graphene is formed on SiC(000-1) surfaces (the so-called C-face of the crystal) by annealing in vacuum, with the resulting films characterized by atomic force microscopy, Auger electron spectroscopy, scanning Auger microscopy and Raman spectroscopy. Morphology ... More
Universal condition for critical percolation thresholds of kagome-like latticesDec 01 2008Jan 13 2009Lattices that can be represented in a kagome-like form are shown to satisfy a universal percolation criticality condition, expressed as a relation between P_3, the probability that all three vertices in the triangle connect, and P_0, the probability that ... More
Electron and hole contributions to normal-state transport in the superconducting system Sn$_{1-x}$In$_x$TeFeb 27 2018Aug 10 2018Indium-doped SnTe has been of interest because the system can exhibit both topological surface states and bulk superconductivity. While the enhancement of the superconducting transition temperature is established, the character of the electronic states ... More
Reconciliation of local and long range tilt correlations in underdoped La2-xBaxCuO4Dec 19 2014A long standing puzzle regarding the disparity of local and long range CuO6 octahedral tilt correlations in the underdoped regime of La2-xBaxCuO4 is addressed by utilizing complementary neutron powder diffraction and inelastic neutron scattering (INS) ... More
Superconductivity induced by In substitution into the topological crystalline insulator Pb(0.5)Sn(0.5)TeMay 30 2014Indium substitution turns the topological crystalline insulator (TCI) Pb$_{0.5}$Sn$_{0.5}$Te into a possible topological superconductor. To investigate the effect of the indium concentration on the crystal structure and superconducting properties of (Pb$_{0.5}$Sn$_{0.5}$)$_{1-x}$In$_{x}$Te, ... More
Local Structure of the Superconductor K0.8Fe1.6+xSe2: Evidence of Large Structural DisorderNov 04 2011The local structure of superconducting single crystals of K0.8Fe1.6+xSe2 with Tc = 32.6 K was studied by x-ray absorption spectroscopy. Near-edge spectra reveal that the average valence of Fe is 2+. The room temperature structure about the Fe, K and Se ... More
Metal-insulator-metal transition in NdNiO3 films capped by CoFe2O4Feb 07 2017Metal-insulator transition features as a transformation, from a highly charge conductive state to another state where charge conductivity is greatly suppressed when decreasing the temperature. Here we demonstrate two consecutive transitions in NdNiO3 ... More
Diagonal charge stripes giving a suppression of spectral weight at selected spots on the Fermi surfaceNov 06 1998Here we report an asymmetric suppresion of spectral weight at the Fermi surface around the M points using angle resolved photoemission spectroscopy. The results provide direct evidence for diagonal stripes in the Bi2212 superconductors.
Laboratory Measurement and Theoretical Modeling of K-shell X-ray Lines from Inner-shell Excited and Ionized Ions of OxygenMar 30 2005We present high resolution laboratory spectra of K-shell X-ray lines from inner-shell excited and ionized ions of oxygen, obtained with a reflection grating spectrometer on the electron beam ion trap (EBIT-I) at the Lawrence Livermore National Laboratory. ... More
Friedel Oscillation-Induced Energy Gap Manifested as Transport Asymmetry at Monolayer-Bilayer Graphene BoundariesJan 08 2014We show that Friedel charge oscillation near an interface opens a gap at the Fermi energy for electrons with wave vectors perpendicular to the interface. If the Friedel gaps on two sides of the interface are different, a nonequlibrium effect - shifting ... More
Stimulation-based control of dynamic brain networksJan 05 2016The ability to modulate brain states using targeted stimulation is increasingly being employed to treat neurological disorders and to enhance human performance. Despite the growing interest in brain stimulation as a form of neuromodulation, much remains ... More
Simplicial Ricci Flow: An Example of a Neck Pinch Singularity in 3DAug 19 2013Apr 28 2014We examine a Type-1 neck pinch singularity in simplicial Ricci flow (SRF) for an axisymmetric piecewise flat 3-dimensional geometry with 3-sphere topology. SRF was recently introduced as an unstructured mesh formulation of Hamilton's Ricci flow (RF). ... More
Crossing on hyperbolic latticesNov 23 2011Jun 05 2012We divide the circular boundary of a hyperbolic lattice into four equal intervals, and study the probability of a percolation crossing between an opposite pair, as a function of the bond occupation probability p. We consider the {7,3} (heptagonal), enhanced ... More
Charge order and low frequency spin dynamics in lanthanum cuprates revealed by Nuclear Magnetic ResonanceJul 02 2010We report detailed 17O, 139La, and 63Cu Nuclear Magnetic Resonance (NMR) and Nuclear Quadrupole Resonance (NQR) measurements in a stripe ordered La1.875Ba0.125CuO4 single crystal and in oriented powder samples of La1.8-xEu0.2SrxCuO4. We observe a partial ... More
Large magnetoresistance in La2/3Ca1/3MnO3 thin films induced by metal masked ion damage techniqueMar 09 2006e have developed a simple process to obtain large magnetoresistance (MR) in perovskite manganite thin films by a combination of focused ion beam (FIB) milling and 120 keV H$_{2}^{+}$ ion implantation. Metal slits about 70 nm in width were printed by 30 ... More
Probing the dynamical state, baryon content, and multiphase nature of galaxy clusters with bright background QSOsOct 09 2018We have initiated a programme to study the physical/dynamical state of gas in galaxy clusters and the impact of the cluster environment on gaseous halos of individual galaxies using X-ray imaging and UV absorption line spectroscopy of background QSOs. ... More
Computing Quasiconformal Maps on Riemann surfaces using Discrete Curvature FlowMay 25 2010Dec 01 2010Surface mapping plays an important role in geometric processing. They induce both area and angular distortions. If the angular distortion is bounded, the mapping is called a {\it quasi-conformal} map. Many surface maps in our physical world are quasi-conformal. ... More
Effect of magnetic field on the spin resonance in FeTe(0.5)Se(0.5) as seen via inelastic neutron scatteringSep 30 2009Mar 26 2010Inelastic neutron scattering and susceptibility measurements have been performed on the optimally-doped Fe-based superconductor FeTe(0.5)Se(0.5), which has a critical temperature, Tc of 14 K. The magnetic scattering at the stripe antiferromagnetic wave-vector ... More
Short-range incommensurate magnetic order near the superconducting phase boundary in Fe(1+d)Te(1-x)Se(x)Jun 20 2009Sep 11 2009We performed elastic neutron scattering and magnetization measurements on Fe(1.07)Te(0.75)Se(0.25) and FeTe(0.7)Se(0.3). Short-range incommensurate magnetic order is observed in both samples. In the former sample with higher Fe content, a broad magnetic ... More
Inhomogeneous spin diffusion of transversely polarized fermions at a high temperature limitJul 10 2016Aug 17 2016We study the transverse spin diffusion of trapped polarized Fermi gases based on the quantum Boltzmann equation. The inhomogeneous dephasing can not completely removed by the echo pulse and might have significant correction to the demagnetization dynamics. ... More
On the cohomology of the Milnor fibre of a hyperplane arrangementJul 15 2013Jul 25 2013We investigate the cohomology of the Milnor fibre of a reflection arrangement as a module for the group $\Gamma$ generated by the reflections, together with the cyclic monodromy. Although we succeed completely only for unitary reflection groups of rank ... More