Results for "J. Orenstein"

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Random walk approach to spin dynamics in a two-dimensional electron gas with spin-orbit couplingJul 31 2010Mar 30 2011We introduce and solve a semi-classical random walk (RW) model that describes the dynamics of spin polarization waves in zinc-blende semiconductor quantum wells. We derive the dispersion relations for these waves, including the Rashba, linear and cubic ... More
Optical non-reciprocity in magnetic structures related to high-Tc superconductorsJan 20 2011Recent neutron scattering [1,2], and optical measurements [3,4] have detected evidence in underdoped cuprate superconductors for a phase transition near the pseudogap onset temperature T* to a time reversal-breaking state. The neutron scattering indicates ... More
Finite-sample Guarantees for Winsorized Importance SamplingOct 25 2018Importance sampling is a widely used technique to estimate the properties of a distribution. The resulting estimator is always unbiased, but may sometimes incur huge variance. This paper investigates trading-off some bias for variance by winsorizing the ... More
Kerr effect as evidence of gyrotropic order in the cupratesDec 11 2012The Kerr effect can arise in a time-reversal invariant dissipative medium that is "gyrotropic", i.e. one that breaks inversion ($\mathcal I$) and all mirror symmetries. Examples of such systems include electron analogs of cholesteric liquid crystals, ... More
Metal-less Metamaterial for Surface Plasmon Polariton guiding and amplificationJul 01 2007We propose a novel metamaterial for Surface Plasmon Polarition guiding, amplification and modulation. Specific example of AlN/GaN Quantum Cascade Amplifier and its dispersion engineering are studied in details. The general original concept of metamaterials ... More
Metal-less Optical Left Handed Material by Low-dimensional Quantum Structure AnisotropyDec 31 2006We propose a novel concept of left-handed metamaterial assembly by semiconductor based low-dimensional quantum structures. We theoretically demonstrate the left-handed material, combined from low-dimensional semiconductor quantum wells or quantum dots. ... More
Confinement-induced Berry phase and helicity-dependent photocurrentsNov 18 2009The photocurrent in an optically active metal is known to contain a component that switches sign with the helicity of the incident radiation. At low frequencies, this current depends on the orbital Berry phase of the Bloch electrons via the "anomalous ... More
Quantized Photocurrents in the Chiral Multifold Fermion System RhSiFeb 08 2019The rapid pace of discovery of new classes of Weyl semimetals is driving a search for properties that derive from their unique bandstructure topology. One of the most striking of the predicted properties is the quantized circular photogalvanic effect ... More
Terahertz time-domain spectroscopy of transient metallic and superconducting statesJun 22 2015Jun 24 2015Time-resolved terahertz time-domain spectroscopy (THz-TDS) is an ideal tool for probing photoinduced nonequilibrium metallic and superconducting states. Here, we focus on the interpretation of the two-dimensional response function $\Sigma(\omega;t)$ that ... More
Berry phase mechanism for optical gyrotropy in stripe-ordered cupratesDec 12 2012Optical gyrotropy, the lifting of degeneracy between left and right circularly polarized light, can be generated by either time-reversal or chiral symmetry breaking. In the high-$T_c$ superconductor La$_{2-x}$Ba$_x$CuO$_4$ (LBCO), gyrotropy onsets at ... More
Observation of Coherent Helimagnons and Gilbert damping in an Itinerant MagnetAug 07 2012We study the magnetic excitations of itinerant helimagnets by applying time-resolved optical spectroscopy to Fe0.8Co0.2Si. Optically excited oscillations of the magnetization in the helical state are found to disperse to lower frequency as the applied ... More
Giant anisotropic nonlinear optical response in transition metal monopnictide Weyl semimetalsSep 16 2016Although Weyl fermions have proven elusive in high-energy physics, their existence as emergent quasiparticles was recently predicted in certain crystalline solids in which either inversion or time-reversal symmetry is broken\cite{WanPRB2011,BurkovPRL2011, ... More
An Exact SU(2) Symmetry and Persistent Spin Helix in a Spin-Orbit Coupled SystemJun 07 2006Spin-orbit coupled systems generally break the spin rotation symmetry. However, for a model with equal Rashba and Dresselhauss coupling constant (the ReD model), and for the $[110]$ Dresselhauss model, a new type of SU(2) spin rotation symmetry is discovered. ... More
Abrupt transition in quasiparticle dynamics at optimal doping in a cuprate superconductor systemMar 15 2005We report time-resolved measurements of the photoinduced change in reflectivity, Delta R, in the Bi2Sr2Ca(1-y)Dy(y)Cu2O(8+delta) (BSCCO) system of cuprate superconductors as a function of hole concentration. We find that the kinetics of quasiparticle ... More
Phase transition beneath the superconducting dome in BaFe$_2$(As$_{1-x}$P$_x$)$_2$Feb 13 2015Jun 11 2015We present a theory for the large suppression of the superfluid-density, $\rho_s$, in BaFe$_2$(As$_{1-x}$P$_x$)$_2$ in the vicinity of a putative spin-density wave quantum critical point at a P-doping, $x=x_{c}$. We argue that the transition becomes weakly ... More
Optical conductivity of a superfluid density waveJan 04 2002We present a calculation of the low frequency optical conductivity of a superconductor in the presence of quenched inhomogeneity in both the superfluid and normal fluid densities. We find that inhomogeneity in the superfluid density displaces spectral ... More
Non-local Ponderomotive Nonlinearity in PlasmonicJul 22 2009We analyze an inherent nonlinearity of Surface Plasmon Polaritons at the interface of Fermi-Dirac metal plasma, stemming from the depletion of electron density in high-field intensity regions. The derived optical nonlinear coefficients are comparable ... More
Regular norm and the operator semi-norm on a non-unital Banach AlgebraOct 31 2014Dec 11 2015We show that if $\mathfrak{A}$ is a commutative complex non-unital Banach Algebra with norm $\|\cdot\|$, then $\|\cdot\|$ is regular on $\mathfrak{A}$ if and only if $\|\cdot\|_{op}$ is a norm on $\mathfrak{A}\oplus \mathbb{C}$ and $\mathfrak{A}\oplus\mathbb{C}$ ... More
Toeplitz Operators on the Generalized Fock Space in Symmetrically Normed IdealsOct 22 2014Nov 28 2014In this paper we will give necessary and sufficient conditions for the operator $T_\nu^s$ to be in the symmetrically normed ideal $\mathcal{C}_\Phi$ for an arbitrary symmetric norming function $\Phi$ where $T_\nu$ is the Toeplitz operator on the generalized ... More
Fredholm operators in the Toeplitz Algebra $\mathcal{I}(QC)$Sep 09 2014May 04 2016We will give a complete description of $\mathcal{I}$, the set of invertible quasicontinuous functions on the unit circle. After doing this, we will then classify the path-connected components of $\mathcal{I}$ and show that $\mathcal{I}$ has uncountably ... More
Toeplitz Operators in a Symmetrically-Normed IdealSep 08 2014May 03 2016We will give necessary and sufficient conditions for a Toeplitz operator $T_\nu$, having a positive Borel measure $\nu$ for a symbol, on the Fock Space (also known as the Segal-Bargmann space) to be in the symmetrically-normed ideal $\mathcal{C}_\Phi$ ... More
Low Temperature AC Conductivity in BSCCO (2212)Aug 26 1999Jan 26 2000We report measurements of anamolously large dissipative conductivities in BiSrCaCuO(2212) at low temperatures. We have measured the complex conductivity of BSCCO thin films at 100-600 GHz as a function of doping from the underdoped to the overdoped state. ... More
Nodal Quasiparticle Lifetime in the Superconducting State of BSCCO(2212)Mar 14 2000Jun 16 2000We have measured the complex conductivity of a BSCCO(2212) thin film between 0.2 and 1.0 THz. We find the conductivity in the superconducting state to be well described as the sum of contributions from quasiparticles, the condensate, and order parameter ... More
Vanishing of phase coherence in underdoped Bi_2Sr_2CaCu_2O_8+dOct 21 1998Aug 25 1999Coherent time-domain spectroscopy is used to measure the screening and dissipation of high-frequency electromagnetic fields in a set of underdoped Bi_2Sr_2CaCu_2O_8+d thin films. The measurements provide direct evidence for a phase-fluctuation driven ... More
Coherent Propagation of Spin Helices in a Quantum-Well Confined Electron GasDec 13 2012We use phase-resolved transient grating spectroscopy to measure the propagation of spin helices in a high mobility $n$-GaAs/AlGaAs quantum well with an applied in-plane electric field. At relatively low fields helical modes crossover from overdamped excitations ... More
Measurement of Transport Lifetime in a Cuprate SuperconductorJun 01 2000Oct 27 2000We report measurements of the phase of the conductivity, $\phi_\sigma\equiv arg(\sigma)$, in the normal state of a $Bi_{2}Sr_{2}CaCu_{2}O_{8+\delta}$ (BSCCO) thin film from 0.2-1.0 THz. From $\phi_\sigma$ we obtain the time delay of the current response, ... More
Doppler velocimetry of spin propagation in a two-dimensional electron gasAug 16 2012Controlling the flow of electrons by manipulation of their spin is a key to the development of spin-based electronics. While recent demonstrations of electrical-gate control in spin-transistor configurations show great promise, operation at room temperature ... More
Measurement of electron-hole friction in an n-doped GaAs/AlGaAs quantum well using optical transient grating spectroscopyMar 30 2011May 26 2011We use phase-resolved transient grating spectroscopy to measure the drift and diffusion of electron-hole density waves in a semiconductor quantum well. The unique aspects of this optical probe allow us to determine the frictional force between a two-dimensional ... More
Observation of spin Coulomb drag in a two-dimensional electron gasDec 01 2005An electron propagating through a solid carries spin angular momentum in addition to its mass and charge. Of late there has been considerable interest in developing electronic devices based on the transport of spin, which offer potential advantages in ... More
Kerr effect as evidence of gyrotropic order in the cuprates - revisitedMay 05 2014Sep 16 2014Recent analysis has confirmed earlier general arguments that the Kerr response vanishes in any time-reversal invariant system which satisfies the Onsager relations. Thus, the widely cited relation between natural optical activity (gyrotropy) and the Kerr ... More
Non-diffusive spin dynamics in a two-dimensional electron gasOct 03 2006We describe measurements of spin dynamics in the two-dimensional electron gas in GaAs/GaAlAs quantum wells. Optical techniques, including transient spin-grating spectroscopy, are used to probe the relaxation rates of spin polarization waves in the wavevector ... More
Photoinduced Changes of Reflectivity in Single Crystals of YBa2Cu3O6.5 (Ortho II)Jul 15 2001We report measurements of the photoinduced change in reflectivity of an untwinned single crystal of YBa2Cu3O6.5 in the ortho II structure. The decay rate of the transient change in reflectivity is found to decrease rapidly with decreasing temperature ... More
Diffusion of Nonequilibrium Quasiparticles in a Cuprate SuperconductorSep 08 2003Sep 10 2003We report a transport study of nonequilibrium quasiparticles in a high-Tc cuprate superconductor using the transient grating technique. Low-intensity laser excitation (at photon energy 1.5 eV) was used to introduce a spatially periodic density of quasiparticles ... More
Fractional power-law conductivity in SrRuO_3 and its consequencesJun 19 2000We combine the results of terahertz time-domain spectroscopy with far-infrared transmission and reflectivity to obtain the conductivity of SrRuO_3 over an unprecedented continuous range in frequency, allowing us to characterize the approach to zero frequency ... More
Optical 3D cavity modes below the diffractionlimit using slow-wave surface-plasmonpolaritonsMay 17 2006Apr 15 2008Modal volumes at the nano-scale, much smaller than the "diffraction-limit", with appreciable quality factors, are calculated for a dielectric cavity embedded in a space between metal plates. The modal field is bounded between the metal interfaces in one ... More
Ultrasmall volume Plasmons - yet with complete retardation effectsApr 15 2008Oct 26 2008Nano particle-plasmons are attributed to quasi-static oscillation with no wave propagation due to their subwavelength size. However, when located within a band-gap medium (even in air if the particle is small enough), the particle interfaces are acting ... More
Plasmon-SolitonMay 17 2006Apr 15 2008Formation of a novel hybrid-vector spatial plasmon-soliton in a Kerr slab embedded in-between metal plates is predicted and analyzed with a modified NLSE, encompassing hybrid vector field characteristics. Assisted by the transverse plasmonic effect, the ... More
Dynamical Interplay between Coexisting Orders in the Electron-Doped Cuprate Superconductor Nd_{2-x}Ce_xCuO_4Aug 04 2012We use coherent pump-probe spectroscopy to measure the photoinduced reflectivity \DeltaR, and complex dielectric function, {\delta}\in, of the electron-doped cuprate superconductor Nd_{2-x}Ce_xCuO_{4+\delta} at a value of x near optimal doping, as a function ... More
Nano plasmon polariton modes of a wedge cross section metal waveguideJun 20 2006Apr 15 2008Optical plasmon-polariton modes confined in both transverse dimensions to significantly less than a wavelength are exhibited in open waveguides structured as sharp metal wedges. The analysis reveals two distinctive modes corresponding to a localized mode ... More
WHOI-Plankton- A Large Scale Fine Grained Visual Recognition Benchmark Dataset for Plankton ClassificationOct 02 2015Planktonic organisms are of fundamental importance to marine ecosystems: they form the basis of the food web, provide the link between the atmosphere and the deep ocean, and influence global-scale biogeochemical cycles. Scientists are increasingly using ... More
Single-quasiparticle stability and quasiparticle-pair decay in YBa2Cu3O6.5 (Ortho II)Sep 04 2003We report results and analysis of time-resolved photoinduced reflectivity experiments on the cuprate superconductor YBa2Cu3O6.5. The sample, which has Tc=45 K, was characterized by a high degree of purity and Ortho II ordering. The change in reflectivity ... More
Optical evidence of broken C$_4$ symmetry across optimal doping in BaFe$_{2}$(As$_{1-x}$P$_x$)$_2$Jul 14 2015Jul 24 2015The isovalently doped high-$T_{\text{c}}$ superconductor BaFe$_2$(As$_{1-x}$P$_x$)$_2$ is characterized by a rich temperature-doping phase diagram, which includes structural, antiferromagnetic, and superconducting phase transitions. In this work, we use ... More
Evidence for effective thermal boundary resistance from magnon/phonon disequilibriumJan 25 2010We use the time-resolved magneto-optical Kerr effect (TRMOKE) to measure the local temperature and heat flow dynamics in ferromagnetic SrRuO3 thin films. After heating by a pump pulse, the film temperature decays exponentially, indicating that the heat ... More
Observation of ferromagnetic resonance in strontium ruthenate (SrRuO3)Dec 03 2008We report the observation of ferromagnetic resonance (FMR) in SrRuO3 using the time-resolved magneto-optical Kerr effect. The FMR oscillations in the time-domain appear in response to a sudden, optically induced change in the direction of easy-axis anistropy. ... More
Photoexcited states of the harmonic honeycomb iridate γ-Li$_2$IrO$_3$Mar 04 2015Oct 06 2015We report equilibrium and nonequilibrium optical measurements on the recently synthesized "harmonic" honeycomb iridate \gamma-Li$_2$IrO$_3$ (LIO), as well as the layered honeycomb iridate Na$_2$IrO$_3$ (NIO). Using Fourier transform infrared microscopy ... More
Antiferromagnetic resonance and terahertz continuum in $α-$RuCl$_3$Apr 24 2017Oct 09 2017We report measurements of optical absorption in the zig-zag antiferromagnet $\alpha$-RuCl$_3$ as a function of temperature, $T$, magnetic field, $B$, and photon energy, $\hbar\omega$ in the range $\sim$ 0.3 to 8.3 meV, using time-domain terahertz spectroscopy. ... More
Determination of the spin-flip time in ferromagnetic SrRuO3 from time-resolved Kerr measurementsAug 03 2010We report time-resolved Kerr effect measurements of magnetization dynamics in ferromagnetic SrRuO3. We observe that the demagnetization time slows substantially at temperatures within 15K of the Curie temperature, which is ~ 150K. We analyze the data ... More
A new collective mode in YBCO observed by time-domain reflectometryMay 07 2013We report the observation of coherent oscillations associated with charge density wave (CDW) order in the underdoped cuprate superconductor YBa2Cu3O6+x by time-resolved optical reflectivity. Oscillations with frequency 1.87 THz onset at approximately ... More
Far-infrared optical conductivity gap in superconducting MgB2 filmsJun 18 2001We report the first study of the optical conductivity of MgB2 covering the range of its superconducting energy gap. Terahertz time-domain spectroscopy is utilized to determine the complex, frequency-dependent conductivity of thin films. The imaginary ... More
Picometer Registration of Zinc Impurity States in Bi2Sr2CaCu2O8+d for Phase Determination in Intra-unit-cell Fourier Transform STMFeb 20 2012Direct visualization of electronic-structure symmetry within each crystalline unit cell is a new technique for complex electronic matter research. By studying the Bragg peaks in Fourier transforms of electronic structure images, and particularly by resolving ... More
Infrared Single-Photon Detector based on Silicon Two-Photon AbsorptionFeb 13 2008We propose a scheme for infrared single-photon detection based on two-photon absorption at room-temperature in Si avalanche photodiodes, where the detected photon's energy is lower than the bandgap and the energy difference is complemented by a pump field. ... More
Optical gyrotropy from axion electrodynamics in momentum spaceMar 09 2015Oct 05 2015Several emergent phenomena and phases in solids arise from configurations of the electronic Berry phase in momentum space that are similar to gauge field configurations in real space such as magnetic monopoles. We show that the momentum-space analogue ... More
Gap plasmon polariton structure for very efficient micro to nano scale interfacingMay 23 2006The seamless transition between micro-scale photonics and nano-scale plasmonics requires the mitigation between different waveguiding mechanisms as well as between few orders of magnitude in the field lateral size, down to a small fraction of a wavelength. ... More
Single DNG Interface Makes a Better Perfect LensJan 01 2013Oct 10 2014We show that a single-interface between regular and double-negative (DNG) media constitutes the core structure of a perfect lens and, furthermore, substantially outperforms the highly discussed DNG slab-based lens under imperfect conditions, maintaining ... More
High-Rate Entanglement Source via Two-Photon Emission from Semiconductor Quantum WellsDec 14 2006May 17 2007We propose a compact high-intensity room-temperature source of entangled photons based on the efficient second-order process of two-photon spontaneous emission from electrically-pumped semiconductor quantum wells in a photonic microcavity. Two-photon ... More
Resonant magneto-optic Kerr effect in the magnetic topological insulator Cr:(Sb$_x$,Bi$_{1-x}$)$_2$Te$_3$May 04 2015Dec 02 2015We report measurements of the polar Kerr effect, proportional to the out-of-plane component of the magnetization, in thin films of the magnetically doped topological insulator $(\text{Cr}_{0.12}\text{Bi}_{0.26}\text{Sb}_{0.62})_2\text{Te}_3$. Measurements ... More
Concave Plasmonic Particles: Broad-Band Geometrical Tunability in the Near Infra-RedJan 21 2010Optical resonances spanning the Near and Short Infra-Red spectral regime were exhibited experimentally by arrays of plasmonic nano-particles with concave cross-section. The concavity of the particle was shown to be the key ingredient for enabling the ... More
Two-Photon Emission from SemiconductorsJan 16 2007Oct 25 2007We report the first experimental observations of two-photon emission from semiconductors, to the best of our knowledge, and develop a corresponding theory for the room-temperature process. Spontaneous two-photon emission is demonstrated in optically-pumped ... More
Negative Group Velocity: Is It a Backward wave or Fast Light?Jul 30 2008When a negative slope of the dispersion curve is encountered, the propagating light may be either 'fast light' or 'backward propagating'. We show that causality considerations select only one of which for each scenario, and demonstrate that the same photonic ... More
Resonance-enhanced optical nonlinearity in the Weyl semimetal TaAsApr 19 2018Apr 20 2018While all media can exhibit first-order conductivity describing current linearly proportional to electric field, $E$, the second-order conductivity, $\sigma^{(2)}$ , relating current to $E^2$, is nonzero only when inversion symmetry is broken. Second ... More
Tuning the electronic properties of J_eff=1/2 correlated semimetal in epitaxial perovskite SrIrO3May 08 2013We investigated the electronic properties of epitaxially stabilized perovskite SrIrO3 and demonstrated the effective strain-control on its electronic structure. Comprehensive transport measurements showed that the strong spin-orbit coupling renders a ... More
Two-phonon coupling to the antiferromagnetic phase transition in multiferroic BiFeO3Dec 03 2007A prominent band centered at around 1000-1300 cm-1 and associated with resonant enhancement of two-phonon Raman scattering is reported in multiferroic BiFeO3 thin films and single crystals. A strong anomaly in this band occurs at the antiferromagnetic ... More
Linearly Dichroic Plasmonic Lens and Hetero-Chiral StructuresMay 31 2014We present theoretical and experimental study of plasmonic Hetero-Chiral structures, comprised of constituents with opposite chirality. We devise, simulate and experimentally demonstrate different schemes featuring selective surface plasmon polariton ... More
Surface Plasmon Polariton Self-Focusing by Ponderomotive ForcesAug 29 2007Nonlinear properties of Surface Plasmon Polaritons stemming from the inherent electron plasma nonlinearity of the metal layers are investigated. A fluid-mechanics plasma model is used to describe the electron motion in metals. The nonlinear ponderomotive ... More
Semiclassical theory of nonlinear magneto-optical responses with applications to topological Dirac/Weyl semimetalsSep 19 2016We study nonlinear magneto-optical responses of metals by a semiclassical Boltzmann equation approach. We derive general formulas for linear and second order nonlinear optical effects in the presence of magnetic fields that include both Berry curvature ... More
Resonances On-Demand for Plasmonic Nano-ParticlesJan 10 2011A method for designing plasmonic particles with desired resonance spectra is presented. The method is based on repetitive perturbations of an initial particle shape while calculating the eigenvalues of the various quasistatic resonances. The method is ... More
Semiclassical theory of nonlinear magneto-optical responses with applications to topological Dirac/Weyl semimetalsSep 19 2016Nov 22 2016We study nonlinear magneto-optical responses of metals by a semiclassical Boltzmann equation approach. We derive general formulas for linear and second order nonlinear optical effects in the presence of magnetic fields that include both Berry curvature ... More
Spin-Charge-Lattice Coupling through Resonant Multi-Magnon Excitations in Multiferroic BiFeO3Mar 24 2008Jan 07 2009Spin-charge-lattice coupling mediated by multi-magnon processes is demonstrated in multiferroic BiFeO3. Experimental evidence of two and three magnons excitations as well as multimagnon coupling at electronic energy scales and high temperatures are reported. ... More
The rate of quasiparticle recombination probes the onset of coherence in cuprate superconductorsJan 20 2016The condensation of an electron superfluid from a conventional metallic state at a critical temperature $T_c$ is described well by the BCS theory. In the underdoped copper-oxides, high-temperature superconductivity condenses instead from a nonconventional ... More
From a single-band metal to a high-temperature superconductor via two thermal phase transitions (Supporting Material)Mar 11 2011In this supporting material for the main paper (the preceding submission), we show, in addition to the related information for the experiments, additional discussion that cannot fit in the main paper (due to the space constraint). It includes further ... More
From a single-band metal to a high-temperature superconductor via two thermal phase transitionsMar 11 2011The nature of the pseudogap phase of cuprate high-temperature superconductors is a major unsolved problem in condensed matter physics. We studied the commencement of the pseudogap state at temperature T* using three different techniques (angle-resolved ... More
Large magneto-optical Kerr effect and imaging of magnetic octupole domains in an antiferromagnetic metalMay 17 2018When a polarized light beam is incident upon the surface of a magnetic material, the reflected light undergoes a polarization rotation. This magneto-optical Kerr effect (MOKE) has been intensively studied in a variety of ferro- and ferrimagnetic materials ... More
Emergence of the persistent spin helix in semiconductor quantum wellsMar 26 2009Mar 28 2009According to Noethers theorem, for every symmetry in nature there is a corresponding conservation law. For example, invariance with respect to spatial translation corresponds to conservation of momentum. In another well-known example, invariance with ... More
Photoinduced changes of the chemical potential in superconducting Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$Oct 21 2015The chemical potential of a superconductor is of critical importance since, at equilibrium, it is the energy where electrons pair and form the superconducting condensate. However, in non-equilibrium measurements, there may be a difference between the ... More
A Hot Saturn Orbiting An Oscillating Late Subgiant Discovered by TESSJan 07 2019We present the discovery of TOI-197.01, the first transiting planet identified by the Transiting Exoplanet Survey Satellite (TESS) for which asteroseismology of the host star is possible. TOI-197 (HIP116158) is a bright (V=8.2 mag), spectroscopically ... More
Tracking Cooper Pairs in a Cuprate Superconductor by Ultrafast Angle-Resolved PhotoemissionJun 11 2012In high-temperature superconductivity, the process that leads to the formation of Cooper pairs, the fundamental charge carriers in any superconductor, remains mysterious. We use a femtosecond laser pump pulse to perturb superconducting Bi2Sr2CaCu2O8+{\delta}, ... More
Linear and Nonlinear Optical constants of BiFeO_3Jan 10 2008Using spectroscopic ellipsometry, the refractive index and absorption versus wavelength of the ferroelectric antiferromagnet Bismuth Ferrite, BiFeO_3 is reported. The material has a direct band-gap at 442 nm wavelength (2.81 eV). Using optical second ... More
Field evolution of magnons in $α$-RuCl$_3$ by high-resolution polarized terahertz spectroscopyJun 03 2018Oct 05 2018The Kitaev quantum spin liquid (KSL) is a theoretically predicted state of matter whose fractionalized quasiparticles are distinct from bosonic magnons, the fundamental excitation in ordered magnets. The layered honeycomb antiferromagnet $\alpha$-RuCl$_3$ ... More
Stability of spherical stellar systems I : Analytical resultsNov 22 1995The so-called ``symplectic method'' is used for studying the linear stability of a self-gravitating collisionless stellar system, in which the particles are also submitted to an external potential. The system is steady and spherically symmetric, and its ... More
Information channel capacity in the field theory estimationDec 26 2012The construction of the information capacity for the vector position parameter in the Minkowskian space-time is presented. This lays the statistical foundations of the kinematical term of the Lagrangian of the physical action for many field theory models, ... More
Vortex matter in mesoscopic superconductorsSep 03 1998Superconducting mesoscopic devices in magnetic fields present novel properties which can only be accounted for by both the quantum confinement of the Cooper pairs and by the interaction between the magnetic-field-induced vortices. Sub-micrometer disks, ... More
Microscopic calculation of the phonon-roton branch in superfluid $^4$HeJul 29 1996Diffusion Monte Carlo results for the phonon-roton excitation branch in bulk liquid $^4$He at zero temperature are presented. The sign problem associated to the excited wave function has been dealt both with the fixed-node approximation and the released-node ... More
Self-consistent Skyrme QRPA for use in axially-symmetric nuclei of arbitrary massMay 31 2010We describe a new implementation of the quasiparticle random phase approximation (QRPA) in axially-symmetric deformed nuclei with Skyrme and volume-pairing energy-density functionals. After using a variety of tests to demonstrate the accuracy of the code ... More
Direct Photon Production in Proton-Nucleus and Nucleus-Nucleus CollisionsJun 01 2011Prompt photons produced in a hard reaction are not accompanied with any final state interaction, either energy loss or absorption. Therefore, besides the Cronin enhancement at medium transverse momenta pT and small isotopic corrections at larger pT, one ... More
Globally controlled fault tolerant quantum computationJul 08 2007We describe a method to execute globally controlled quantum information processing which admits a fault tolerant quantum error correction scheme. Our scheme nominally uses three species of addressable two-level systems which are arranged in a one dimensional ... More
Superballistic Diffusion of Entanglement in Disordered Spin ChainsJun 06 2005Sep 12 2005We study the dynamics of a single excitation in an infinite XXZ spin chain, which is launched from the origin. We study the time evolution of the spread of entanglement in the spin chain and obtain an expression for the second order spatial moment of ... More
Strangeness and Quark Gluon PlasmaMay 25 2003A brief summary of strangeness mile stones is followed by a chemical non-equilibrium statistical hadronization analysis of strangeness results at SPS and RHIC. Strange particle production in AA interactions at \sqrt{s_{NN}}\ge 8.6 GeV can be understood ... More
Breakdown of step-flow growth in unstable homoepitaxyJan 13 2004Two mechanisms for the breakdown of step flow growth, in the sense of the appearance of steps of opposite sign to the original vicinality, are studied by kinetic Monte Carlo simulations and scaling arguments. The first mechanism is the nucleation of islands ... More
What does the CCFR measurement of the Gross--Llewelyn Smith sum rule tell us?Oct 14 1994Oct 18 1994Recently the CCFR Collaboration reported the measurement of the Gross--Llewellyn Smith sum rule %at $Q^2=3\; \mr{GeV}^2$: $\int^{1}_{0}\mr{d}F_{3}^{\nu p+\bare{\nu}p}(x,Q^2=3\;\mr{GeV}^2)= 2.50\pm 0.018(\mr{stat})$. Subsequently Kataev and Sidorov analyzed ... More
Parton-Hadron duality in event generatorsAug 28 1992Sep 04 1992The validity of local parton-hadron duality within the framework of HERWIG and JETSET event generators is investigated. We concentrate on ${\rm e}^{+}{\rm e}^{-}$ annihilations in LEP 2 energy range as these interactions provide theoretically the cleanest ... More
Accretion by GalaxiesMar 14 2000Both theory and observation indicate that galaxies like the Milky Way accrete matter at the rate of a few Msun per year.
Complexity fits the fittestDec 11 2012In this paper we shall relate computational complexity to the principle of natural selection. We shall do this by giving a philosophical account of complexity versus universality. It seems sustainable to equate universal systems to complex systems or ... More
Quantum field effects in coupled atomic and molecular Bose-Einstein condensatesJun 21 2001This paper examines the parameter regimes in which coupled atomic and molecular Bose-Einstein condensates do not obey the Gross-Pitaevskii equation. Stochastic field equations for coupled atomic and molecular condensates are derived using the functional ... More
Interaction of antiprotons with nucleiOct 26 2015We performed fully self-consistent calculations of $\bar{p}$-nuclear bound states using a complex ${\bar p}$-nucleus potential accounting for $\bar{p}$-atom data. While the real part of the potential is constructed within the relativistic mean-field (RMF) ... More
Stability of the lattice formed in first-order phase transitions to matter containing strangeness in protoneutron starsApr 18 2002Well into the deleptonization phase of a core collapse supernova, a first-order phase transition to matter with macroscopic strangeness content is assumed to occur and lead to a structured lattice defined by negatively charged strange droplets. The lattice ... More
A Cartier-Gabriel-Kostant structure theorem for Hopf algebroidsDec 29 2010In this paper we give an extension of the Cartier-Gabriel-Kostant structure theorem to Hopf algebroids.
Composite resonances and their impact on the EW chiral LagrangianNov 12 2015In this talk we study the low-energy effective couplings generated by strongly-coupled electroweak models that contain heavy composite resonances. Invariance under $SU(2)_L\times SU(2)_R$ is a key ingredient in the construction of the resonance action. ... More
Hausdorff dimension of boundaries of self-affine tiles in R^nJan 15 1997We present a new method to calculate the Hausdorff dimension of a certain class of fractals: boundaries of self-affine tiles. Among the interesting aspects are that even if the affine contraction underlying the iterated function system is not conjugated ... More
Can stellar wobble in triple systems mimic a planet?Sep 13 2005The first extrasolar planets have been detected by the measurement of the wobble of the parent star. This wobble leads to the periodic modulation of three observables: the radial velocity, the position on the sky and the time of arrival of periodic signals. ... More
A Noncommutative Extension of GravityJul 22 1993The commutative algebra of functions on a manifold is extended to a noncommutative algebra by considering its tensor product with the algebra of nxn complex matrices. Noncommutative geometry is used to formulate an extension of the Einstein-Hilbert action. ... More