Results for "A. Brinkman"

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Structure-Property Relation of SrTiO3-LaAlO3 InterfacesSep 05 2008A large variety of transport properties have been observed at the interface between the insulating oxides SrTiO3 and LaAlO3 such as insulation, 2D interface metallicity, 3D bulk metallicity, Kondo scattering, magnetism and superconductivity. The relation ... More
Electron-hole coupling in high-Tc cuprate superconductorsMar 15 2005Jun 07 2005From recent Hall effect measurements and angle-resolved photo-emission spectroscopy the interesting picture emerges of co-existing hole- and electron-like quasiparticle bands, both in electron- and hole-doped superconducting cuprates. We reflect on the ... More
Nonlocal Cooper pair Splitting in a pSn JunctionDec 16 2011Perfect Cooper pair splitting is proposed, based on crossed Andreev reflection (CAR) in a p-type semiconductor - superconductor - n-type semiconductor (pSn) junction. The ideal splitting is caused by the energy filtering that is enforced by the bandstructure ... More
Crossed Andreev reflection in diffusive contactsNov 06 2006Crossed Andreev reflection in multiterminal structures in the diffusive regime is addressed within the quasiclassical Keldysh-Usadel formalism. The elastic cotunneling and crossed Andreev reflection of quasiparticles give nonlocal currents and voltages ... More
Coherent effects in double-barrier Josephson junctionsDec 07 1999The general solution for ballistic electronic transport through double-barrier Josephson junctions is derived. We show the existence of a regime of phase-coherent transport in which the supercurrent is proportional to the single barrier transparency and ... More
Band offsets and density of Ti3+ states probed by X-ray photoemission on LaAlO3/SrTiO3 heterointerfaces and their LaAlO3 and SrTiO3 bulk precursorsNov 23 2012A set of LaAlO3/SrTiO3 (LAO-STO) interfaces has been probed by X-ray photoemission spectroscopy in order to contrast and compare the effects of LAO overlayer thickness and of the growth conditions on the electronic properties of these heterostructures. ... More
Conductance anisotropy and linear magnetoresistance in La2-xSrxCuO4 thin filmsMay 29 2011We have performed a detailed study of conductance anisotropy and magnetoresistance (MR) of La2-xSrxCuO4 (LSCO) thin films (0.10 < x < 0.25). These two observables are promising for the detection of stripes. Subtle features of the conductance anisotropy ... More
Observability of surface Andreev bound states in a topological insulator in proximity to an s-wave superconductorMar 20 2015Jun 18 2015To guide experimental work on the search for Majorana zero-energy modes, we calculate the superconducting pairing symmetry of a three-dimensional topological insulator in combination with an s-wave superconductor. In analogy to the case of nanowires with ... More
Andreev bound states and current-phase relations in three-dimensional topological insulatorsFeb 18 2013To guide the search for the Majorana fermion, we theoretically study superconductor/topological/superconductor (S/TI/S) junctions in an experimentally relevant regime. We find that the striking features present in these systems, including the doubled ... More
The proximity effect in normal metal - multiband superconductor hybrid structuresJan 28 2004A theory of the proximity effect in normal metal - multiband superconductor hybrid structures is formulated within the quasiclassical Green's function formalism. It is shown that the existence of multiple superconducting bands manifests itself as the ... More
Long range spin supercurrents in ferromagnetic CrO$_2$ using a multilayer contact structureNov 24 2011e report measurements of long ranged supercurrents through ferromagnetic and fully spin-polarized CrO$_2$ deposited on TiO$_2$ substrates. In earlier work, we found supercurrents in films grown on sapphire but not on TiO$_2$. Here we employed a special ... More
Thermodynamics of an incommensurate quantum crystalJul 27 2005Oct 07 2005We present a simple theory of the thermodynamics of an incommensurate quantum solid. The ground state of the solid is assumed to be an incommensurate crystal, with quantum zero-point vacancies and interstitials and thus a non-integer number of atoms per ... More
A Drift-Diffusion-Reaction Model for Excitonic Photovoltaic Bilayers: Asymptotic Analysis and A 2-D HDG Finite-Element SchemeFeb 03 2012We present and discuss a mathematical model for the operation of bilayer organic photovoltaic devices. Our model couples drift-diffusion-recombination equations for the charge carriers (specifically, electrons and holes) with a reaction-diffusion equation ... More
Discrete Breathers in Josephson LaddersFeb 12 2001We present a study of nonlinear localized excitations called discrete breathers in a superconducting array. These localized solutions were recently observed in Josephson-junction ladder arrays by two different experimental groups. We review the experiments ... More
Microscopic nonequilibrium theory of double-barrier Josephson junctionsOct 17 2003We study nonequilibrium charge transport in a double-barrier Josephson junction, including nonstationary phenomena, using the time-dependent quasiclassical Keldysh Green's function formalism. We supplement the kinetic equations by appropriate time-dependent ... More
Nonlocal Andreev reflection, fractional charge and current-phase relation in topological bilayer exciton condensate junctionsJul 08 2014We study Andreev reflection and Josephson currents in topological bilayer exciton condensates (TEC). These systems can create 100% spin entangled nonlocal currents with high amplitudes due to perfect nonlocal Andreev reflection. This Andreev reflection ... More
Ultraviolet images of Seyfert galaxies from the Optical Monitor on XMM-NewtonJun 19 2002The Optical Monitor telescope (Mason et al. 2001) on XMM-Newton provides an exciting multi-wavelength dimension to observations of Active Galactic Nuclei. Here we present ultraviolet images, taken with the OM UVW2 filter (140-270 nm), of various Seyfert ... More
Multiband model for penetration depth in MgB2May 08 2002The results of first principles calculations of the electronic structure and the electron-phonon interaction in MgB2 are used to study theoretically the temperature dependence and anisotropy of the magnetic field penetration depth. The effects of impurity ... More
Andreev spectra and subgap bound states in multiband superconductorsDec 30 2008Aug 14 2009The theory of Andreev conductance is formulated for junctions involving normal metals (N) and multiband superconductors (S) and applied to the case of superconductors with nodeless extended $s_{\pm}$-wave order parameter symmetry, as possibly realized ... More
X-ray absorption lines in the Seyfert 1 galaxy NGC 5548 discovered with Chandra-LETGSFeb 17 2000We present for the first time a high-resolution X-ray spectrum of a Seyfert galaxy. The Chandra-LETGS spectrum of NGC 5548 shows strong, narrow absorption lines from highly ionised species (the H-like and He-like ions of C, N, O, Ne, Na, Mg, Si, as well ... More
Superconducting Quantum Interference Device based on MgB2 nanobridgesMay 28 2001The recently discovered superconductor MgB2, with a transition temperature of 39K, has significant potential for future electronics. An essential step is the achievement of Josephson circuits, of which the superconducting quantum interference device (SQUID) ... More
Superconducting Mg-B films by pulsed laser deposition in an in-situ two-step process using multi-component targetsMar 26 2001Superconducting thin films have been prepared in a two-step in-situ process, using the Mg-B plasma generated by pulsed laser ablation. The target was composed of a mixture of Mg and MgB2 powders to compensate for the volatility of Mg and therefore to ... More
Dominant $s$-wave superconducting gap in PdTe$_2$ observed by tunneling spectroscopy on side-junctionsJan 14 2019Jan 31 2019We have fabricated superconductor-normal metal side-junctions with different barrier transparencies out of PdTe$_2$ crystalline flakes and measured the differential conductance spectra. Modeling our measurements using a modified Blonder Tinkham Klapwijk ... More
In search for the superconducting spin-switch: Magnetization induced resistance switching effects in La$_{0.67}$Sr$_{0.33}$MnO$_3$/YBa$_2$Cu$_3$O$_{7-δ}$ bi- and trilayersMar 17 2009We have studied the influence of the magnetization on the superconducting transition temperature ($T_c$) in bi- and trilayers consisting of the half-metallic ferromagnet La$_{0.67}$Sr$_{0.33}$MnO$_3$ (LSMO) and the high-temperature superconductor YBa$_2$Cu$_3$O$_{7-\delta}$ ... More
Gate-tunable transport properties of in-situ capped Bi$_2$Te$_3$ topological insulator thin filmsApr 13 2016Combining the ability to prepare high-quality, intrinsic Bi$_2$Te$_3$ topological insulator thin films of low carrier density with in-situ protective capping, we demonstrate a pronounced, gate-tunable change in transport properties of Bi$_2$Te$_3$ thin ... More
The Chandra LETGS high resolution X-ray spectrum of the isolated neutron star RX J1856.5-3754Sep 21 2001We present the Chandra LETGS X-ray spectrum of the nearby (~60 pc) neutron star RX J1856.5-3754. Detailed spectral analysis of the combined X-ray and optical data rules out the nonmagnetic neutron star atmosphere models with hydrogen, helium, iron and ... More
High-Resolution spectroscopy of the low-mass X-ray binary EXO 0748-67Oct 31 2000We present initial results from observations of the low-mass X-ray binary EXO 0748-67 with the Reflection Grating Spectrometer on board the XMM-Newton Observatory. The spectra exhibit discrete structure due to absorption and emission from ionized neon, ... More
Optimizing the Majorana character of SQUIDs with topologically non-trivial barriersJun 25 2012We have modeled SQUIDs with topologically non-trivial superconducting junctions and performed an optimization study on the Majorana fermion detection. We find that the SQUID parameters beta_L, and beta_C can be used to increase the ratio of Majorana tunneling ... More
Geometric dependence of Nb-Bi${_2}$Te${_3}$-Nb topological Josephson junction transport parametersAug 05 2014Superconductor-topological insulator-superconductor Josephson junctions have been fabricated in order to study the width dependence of the critical current, normal state resistance and flux periodicity of the critical current modulation in an external ... More
Experimental realization of SQUIDs with topological insulator junctionsDec 26 2011We demonstrate topological insulator (Bi$_2$Te$_3$) dc SQUIDs, based on superconducting Nb leads coupled to nano-fabricated Nb-Bi$_2$Te$_3$-Nb Josephson junctions. The high reproducibility and controllability of the fabrication process allows the creation ... More
Magnetotransport and induced superconductivity in Bi based three-dimensional topological insulatorsDec 10 2012The surface of a 3D topological insulator is conducting and the topologically nontrivial nature of the surface states is observed in experiments. It is the aim of this paper to review and analyze experimental observations with respect to the magnetotransport ... More
Multiband model for tunneling in MgB2 junctionsNov 07 2001May 13 2002A theoretical model for quasiparticle and Josephson tunneling in multiband superconductors is developed and applied to MgB2-based junctions. The gap functions in different bands in MgB2 are obtained from an extended Eliashberg formalism, using the results ... More
Aluminium-26 from massive binary stars I: non-rotating modelsSep 10 2019Aluminium-26 is a short-lived radionuclide with a half-life of 0.72Myr, which is observed today in the Galaxy via gamma-ray spectroscopy and is inferred to have been present in the early Solar System via analysis of meteorites. Massive stars are considered ... More
Thermally excited multi-band conduction in LaAlO3/SrTiO3 heterostructures exhibiting magnetic scatteringNov 22 2013Magnetotransport measurements of charge carriers at the interface of a LaAlO3/SrTiO3 heterostructure with 26 unit cells of LaAlO3 show Hall resistance and magnetoresistance which at low and high temperatures is described by a single channel of electron-like ... More
Transport and thermoelectric properties of the LaAlO$_3$/SrTiO$_3$ interfaceJul 28 2014Mar 30 2015The transport and thermoelectric properties of the interface between SrTiO$_3$ and a 26-monolayer thick LaAlO$_3$-layer grown at high oxygen-pressure have been investigated at temperatures from 4.2 K to 100 K and in magnetic fields up to 18 T. For $T>$ ... More
Confronting atomic data with Fe L-shell spectra of stellar coronaeJun 25 2001It is common to suggest the uncertainties in the atomic data for explaining difficulties that arise in interpreting astrophysical x-ray spectra. The atomic data for the Fe L-shell ions have, over the years, been considered particularly suspect. In this ... More
Correlation between Superconductivity, Band Filling and Electron Confinement at the LaAlO$_{3}$-SrTiO$_{3}$ InterfaceJan 09 2018May 24 2018By combined top- and backgating, we explore the correlation of superconductivity with band filling and electron confinement at the LaAlO$_3$-SrTiO$_3$ interface. We find that the top- and backgate voltages have distinctly different effects on the superconducting ... More
Gate-tunable band structure of the LaAlO$_3$-SrTiO$_3$ interfaceOct 07 2016The 2-dimensional electron system at the interface between LaAlO$_{3}$ and SrTiO$_{3}$ has several unique properties that can be tuned by an externally applied gate voltage. In this work, we show that this gate-tunability extends to the effective band ... More
A physically consistent model for X-ray emission by Seyfert 2 galaxies demonstrated on NGC 1068Jun 21 2001Preliminary analysis of the X-ray spectrum of NGC 1068 obtained by the RGS spectrometer on board XMM-Newton is presented. A physically consistent model is developed in order to quantitatively describe the reprocessing of the central AGN continuum source ... More
Soft X-ray emission lines from a relativistic accretion disk in MCG -6-30-15 and Mrk 766Nov 08 2000XMM-Newton Reflection Grating Spectrometer (RGS) spectra of the Narrow Line Seyfert 1 galaxies MCG -6-30-15 and Mrk 766 are physically and spectroscopically inconsistent with standard models comprising a power-law continuum absorbed by either cold or ... More
Magnetoresistance from broken spin helicityDec 12 2014The propensity of some materials and multilayers to have a magnetic field dependent resistance, called magnetoresistance, has found commercial applications such as giant magnetoresistance harddisk read heads. But magnetoresistance can also be a powerful ... More
Studies of the temperature and frequency dependent impedance of an electroceramic functional oxide thermistorApr 25 2007The charge transport mechanism and the macroscopic dielectric constant in polycrystalline device materials commonly exhibit several components such as electrode-sample interface, grain boundary and bulk contributions. In order to gain precise understanding ... More
How strongly correlated is MnSi?Jan 23 2006We present an experimental study of the electronic structure of MnSi. Using X-ray Absorption Spectroscopy, X-ray photoemission and X-ray fluorescence we provide experimental evidence that MnSi has a mixed valence ground state. We show that self consistent ... More
X-ray spectroscopy of NGC 5548Feb 26 2002We analyze the high-resolution X-ray spectrum of the Seyfert 1 galaxy NGC 5548, for the full 0.1-10 keV band, using improved calibration results of the Chandra-LETGS instrument. The warm absorber consists of at least three ionization components, namely ... More
Conduction spectroscopy of a proximity induced superconducting topological insulatorJul 12 2017The combination of superconductivity and the helical spin-momentum locking at the surface state of a topological insulator (TI) has been predicted to give rise to p-wave superconductivity and Majorana bound states. The superconductivity can be induced ... More
Interaction between counter-propagating quantum Hall edge channels in the 3D topological insulator BiSbTeSe$_2$Jul 21 2017The quantum Hall effect is studied in the topological insulator BiSbTeSe$_2$. By employing top- and back-gate electric fields at high magnetic field, the Landau levels of the Dirac cones in the top and bottom topological surface states can be tuned independently. ... More
Andreev reflection in s-type superconductor proximized 3D topological insulatorApr 01 2016Aug 29 2016We investigate transport and shot noise in lateral N-TI-S contacts, where N is a normal metal, TI is a Bi-based three dimensional topological insulator (3D TI), and S is an s-type superconductor. In normal state, the devices are in the elastic diffusive ... More
Soft X-ray Spectroscopy of Seyfert 2 GalaxiesJul 12 2001Soft X-ray spectroscopy of Seyfert 2 galaxies offers perhaps the best method to probe the possible connection between AGN activity and star formation. Obscuration of powerful radiation from the inferred nucleus allows for detailed study of circumnuclear ... More
High Resolution X-ray Spectroscopy of Seyfert 2 GalaxiesJul 12 2001X-ray spectroscopy of Seyfert 2 galaxies provides an excellent probe of the circumnuclear environment in active galactic nuclei. The grating experiments on both Chandra and XMM-Newton have now provided the first high resolution spectra of several of the ... More
Josephson supercurrent through a topological insulator surface stateDec 15 2011Topological insulators are characterized by an insulating bulk with a finite band gap and conducting edge or surface states, where charge carriers are protected against backscattering. These states give rise to the quantum spin Hall effect without an ... More
Conductance spectroscopy of a proximity induced superconducting topological insulatorJun 19 2015We study the proximity effect between the fully-gapped region of a topological insulator in direct contact with an s-wave superconducting electrode (STI) and the surrounding topological insulator flake (TI) in Au/Bi$_{1.5}$Sb$_{0.5}$Te$_{1.7}$Se$_{1.3}$/Nb ... More
XMM-Newton Reflection Grating Spectrometer Observations of Discrete Soft-X-ray Emission Features from NGC 1068Mar 19 2002Apr 11 2002We present the first high-resolution, soft-X-ray spectrum of the prototypical Seyfert 2 galaxy, NGC 1068. This spectrum was obtained with the XMM-Newton Reflection Grating Spectrometer. Emission lines from H-like and He-like low-Z ions (from C to Si) ... More
Strong magnetic pair breaking in Mn substituted MgB_2 single crystalsOct 10 2005Oct 24 2005Magnetic ions (Mn) were substituted in MgB_2 single crystals resulting in a strong pair-breaking effect. The superconducting transition temperature, T_c, in Mg_{1-x}Mn_xB_2 has been found to be rapidly suppressed at an initial rate of 10 K/%Mn, leading ... More
Electronically coupled complementary interfaces between perovskite band insulatorsMar 04 2006Perovskite oxides exhibit a plethora of exceptional electronic properties, providing the basis for novel concepts of oxide-electronic devices. The interest in these materials is even extended by the remarkable characteristics of their interfaces. Studies ... More
Magnetic effects at the interface between nonmagnetic oxidesMar 01 2007Jun 04 2007The electronic reconstruction at the interface between two insulating oxides can give rise to a highly-conductive interface. In analogy to this remarkable interface-induced conductivity we show how, additionally, magnetism can be induced at the interface ... More
Josephson effect in a few-hole quantum dotSep 22 2018We use a Ge-Si core-shell nanowire to realise a Josephson field-effect transistor with highly transparent contacts to superconducting leads. By changing the electric field we gain access to two distinct regimes not combined before in a single device: ... More
Complex resonance absorption structure in the X-ray spectrum of IRAS13349+2438Oct 31 2000The luminous infrared-loud quasar IRAS 13349+2438 was observed with the XMM-Newton Observatory as part of the Performance Verification program. The spectrum obtained by the Reflection Grating Spectrometer (RGS) exhibits broad (v ~ 1400 km/s FWHM) absorption ... More
Multiple Andreev reflections and Shapiro steps in a Ge-Si nanowire Josephson junctionAug 20 2019We present a Josephson junction based on a Ge-Si core-shell nanowire with transparent superconducting Al contacts, a building block which could be of considerable interest for investigating Majorana bound states, superconducting qubits and Andreev (spin) ... More
The Soft X-ray Spectrum from NGC 1068 Observed with LETGS on ChandraNov 18 2002Using the combined spectral and spatial resolving power of the Low Energy Transmission Grating (LETGS) on board Chandra, we obtain separate spectra from the bright central source of NGC 1068 (Primary region), and from a fainter bright spot 4" to the NE ... More
Ballistic supercurrent discretization and micrometer-long Josephson coupling in germaniumAug 02 2018We fabricate Josephson field-effect-transistors in germanium quantum wells contacted by superconducting aluminum and demonstrate supercurrents carried by holes that extend over junction lengths of several micrometers. In superconducting quantum point ... More
High Resolution Spectroscopy of the X-ray Photoionized Wind in Cygnus X-3 with the Chandra High Energy Transmission Grating SpectrometerFeb 16 2000We present a preliminary analysis of the 1--10 keV spectrum of the massive X-ray binary Cyg X-3, obtained with the High Energy Transmission Grating Spectrometer on the Chandra X-ray Observatory. The source reveals a richly detailed discrete emission spectrum, ... More
Coronal density diagnostics with Helium-like triplets: CHANDRA--LETGS observations of Algol, Capella, Procyon, Eps Eri, Alpha Cen A&B, UX Ari, AD Leo, YY Gem, and HR1099Sep 02 2002We present an analysis of ten cool stars (Algol, Capella, Procyon, Eps Eri, Alpha Cen A&B, UX Ari, AD Leo, YY Gem, and HR1099) observed with the Low Energy Transmission Grating Spectrometer (LETGS) on board the Chandra X-ray Observatory. This sample contains ... More
Orbital reconstruction and two-dimensional electron gas at the LaAlO3/SrTiO3 interfaceDec 08 2008Conventional two-dimensional electron gases are realized by engineering the interfaces between semiconducting compounds. In 2004, Ohtomo and Hwang discovered that an electron gas can be also realized at the interface between large gap insulators made ... More
A First Look at White Dwarf - M Dwarf Pairs in the Sloan Digital Sky Survey (SDSS)Feb 19 2003We have identified 109 White Dwarf (WD) - M dwarf pairs in the Sloan Digital Sky Survey (SDSS) with g < 20th magnitude. For each system we determined the temperature of the WD primary and the spectral type of the M dwarf secondary. Using H-alpha emission ... More
Critical behavior at the dynamic Mott transitionAug 23 2014Aug 28 2014We investigate magnetoresistance of a square array of superconducting islands placed on a normal metal, which offers a unique tunable laboratory for realizing and exploring quantum many-body systems and their dynamics. A vortex Mott insulator where magnetic ... More
Scaling Universality at the Dynamic Vortex Mott TransitionAug 01 2017The dynamic Mott insulator-to-metal transition (DMT) is key to many intriguing phenomena in condensed matter physics yet it remains nearly unexplored. The cleanest way to observe DMT, without the interference from disorder and other effects inherent to ... More
$4π$ periodic Andreev bound states in a Dirac semimetalJul 11 2017Electrons in a Dirac semimetals possess linear dispersion in all three spatial dimensions, and form part of a developing platform of novel quantum materials. Bi$_{1-x}$Sb$_x$ supports a three-dimensional Dirac cone at the Sb-induced band inversion point. ... More
Non-local signatures of the chiral magnetic effect in Dirac semimetal Bi$_{0.97}$Sb$_{0.03}$Jan 31 2019The field of topological materials science has recently been focussing on three-dimensional Dirac semimetals, which exhibit robust Dirac phases in the bulk. However, the absence of characteristic surface states in accidental Dirac semimetals (DSM) makes ... More
A High Resolution Spectroscopic Observation of CAL 83 with XMM-Newton/RGSNov 02 2000We present the first high resolution photospheric X-ray spectrum of a Supersoft X-ray Source, the famous CAL~83 in the Large Magellanic Cloud. The spectrum was obtained with the Reflection Grating Spectrometer on XMM-Newton during the Calibration/Performance ... More
Faint High-Latitude Carbon Stars Discovered by the Sloan Digital Sky Survey: An Initial CatalogFeb 04 2004Feb 06 2004A search of more than 3,000 square degrees of high latitude sky by the Sloan Digital Sky Survey has yielded 251 faint high-latitude carbon stars (FHLCs), the large majority previously uncataloged. We present homogeneous spectroscopy, photometry, and astrometry ... More
Upper limit to magnetism in LaAlO3/SrTiO3 heterostructuresSep 06 2011Using polarized neutron reflectometry (PNR) we measured the neutron spin dependent reflectivity from four LaAlO3/SrTiO3 superlattices. This experiment implies that the upper limit for the magnetization induced by an 11 T magnetic field at 1.7 K is 2 emu/cm3. ... More
Soft X-ray Spectra of Seyfert 2 GalaxiesJul 18 2002High resolution spectroscopic observations of Seyfert galaxies with Chandra and XMM-Newton allows us to study the detailed ionization and thermal structures of the X-ray absorbing/emitting material in the circumnuclear environment. The vast improvement ... More
Dynamic Facial Expression of Emotion Made EasyNov 19 2012Facial emotion expression for virtual characters is used in a wide variety of areas. Often, the primary reason to use emotion expression is not to study emotion expression generation per se, but to use emotion expression in an application or research ... More
"New Zero-Resistance State" in Heterojunctions: A Dynamical EffectFeb 06 2003Feb 28 2003In this paper we discuss some general concepts regarding the recent experiments of Mani et al and Zudov et al regarding the appearance of large resistance variations in the presence of a rf field. The possibility of negative resistance is also discussed. ... More
Investigation of the Mode-Switching Phenomenon in Pulsar B0329+54 Through Polarimetric AnalysisJan 24 2019The phenomenon of profile mode switching in pulsars, where the stable average pulse profile changes to another stable state on the timescale of a pulsar's period, remains poorly understood. We sought to understand how pulsars undergo profile mode switching ... More
Superconducting thin films of MgB2 on (001)-Si by pulsed laser depositionMar 08 2001Superconducting thin films have been prepared on Si-substrates, using pulsed laser deposition from a target composed of a mixture of Mg and MgB2 powders. The films were deposited at room temperature and post-annealed at 600 degrees C. The zero resistance ... More
Josephson supercurrent in a topological insulator without a bulk shuntJun 30 2014A Josephson supercurrent has been induced into the three-dimensional topological insulator Bi1.5Sb0.5Te1.7Se1.3. We show that the transport in Bi1.5Sb0.5Te1.7Se1.3 exfoliated flakes is dominated by surface states and that the bulk conductivity can be ... More
Quantum oscillations and subband properties of the two-dimensional electron gas at the LaAlO3/SrTiO3 interfaceJul 30 2012We have performed high field magnetotransport measurements to investigate the interface electron gas in LaAlO3/SrTiO3 heterostructures. Shubnikov-de Haas oscillations reveal several 2D conduction subbands with carrier effective masses between 1 and 3 ... More
Optically excited multi-band conduction in LaAlO3/SrTiO3 heterostructuresNov 20 2012The low-temperature resistance of a conducting LaAlO3/SrTiO3 interface with a 10 nm thick LaAlO3 film decreases by more than 50% after illumination with light of energy higher than the SrTiO3 band-gap. We explain our observations by optical excitation ... More
In-situ spectroscopy of intrinsic Bi2Te3 topological insulator thin films and impact of extrinsic defectsFeb 04 2015May 26 2015Combined in-situ x-ray photoemission spectroscopy, scanning tunnelling spectroscopy and angle resolved photoemission spectroscopy of molecular beam epitaxy grown Bi2Te3 on lattice mismatched substrates reveal high quality stoichiometric thin films with ... More
Magnetoresistance oscillations and relaxation effects at the SrTiO3-LaAlO3 interfaceJun 27 2008We present low-temperature and high-field magnetotransport data on SrTiO3-LaAlO3 interfaces. The resistance shows hysteresis in magnetic field and a logarithmic relaxation as a function of time. Oscillations in the magnetoresistance are observed, showing ... More
Soft X-ray Spectroscopy of NGC 1068 with XMM-Newton RGS and Chandra LETGSMar 02 2002Mar 06 2002We present high-resolution soft-X-ray spectra of the prototypical Seyfert 2 galaxy, NGC 1068, taken with XMM-Newton RGS and Chandra LETGS. Its rich emission-line spectrum is dominated by recombination in a warm plasma (bright, narrow radiative recombination ... More
Hard superconducting gap and diffusion-induced superconductors in Ge-Si nanowiresJul 11 2019We show a hard induced superconducting gap in a Ge-Si nanowire Josephson transistor up to in-plane magnetic fields of $250$ mT, an important step towards creating and detecting Majorana zero modes in this system. A hard induced gap requires a highly homogeneous ... More
Hard superconducting gap and diffusion-induced superconductors in Ge-Si nanowiresJul 11 2019Jul 15 2019We show a hard induced superconducting gap in a Ge-Si nanowire Josephson transistor up to in-plane magnetic fields of $250$ mT, an important step towards creating and detecting Majorana zero modes in this system. A hard induced gap requires a highly homogeneous ... More
Can a Dusty Warm Absorber Model Reproduce the Soft X-ray Spectra of MCG-6-30-15 and Mrk 766?Dec 19 2001Jun 25 2003XMM-Newton RGS spectra of MCG-6-30-15 and Mrk 766 exhibit complex discrete structure, which was interpreted in a paper by Branduardi-Raymont et al. (2001) as evidence for the existence of relativistically broadened Lyman alpha emission from carbon, nitrogen, ... More
Parallel electron-hole bilayer conductivity from electronic interface reconstructionDec 23 2009Apr 06 2010The perovskite SrTiO$_3$-LaAlO$_3$ structure has advanced to a model system to investigate the rich electronic phenomena arising at polar interfaces. Using first principles calculations and transport measurements we demonstrate that an additional SrTiO$_3$ ... More
Simultaneous UV and X-ray Spectroscopy of the Seyfert 1 Galaxy NGC 5548. I. Physical Conditions in the UV AbsorbersMay 09 2003We present new UV spectra of the nucleus of the Seyfert 1 galaxy NGC 5548, which we obtained with the Space Telescope Imaging Spectrograph at high spectral resolution, in conjunction with simultaneous Chandra X-ray Observatory spectra. Taking advantage ... More
Candidate spectroscopic binaries in the Sloan Digital Sky SurveyAug 29 2005We have examined the radial velocity data for stars spectroscopically observed by the Sloan Digital Sky Survey (SDSS) more than once to investigate the incidence of spectroscopic binaries, and to evaluate the accuracy of the SDSS stellar radial velocities. ... More
Low carrier concentration crystals of the topological insulator Bi$_{2-x}$Sb$_{x}$Te$_{3-y}$Se$_{y}$: a magnetotransport studyNov 10 2014May 07 2015In 3D topological insulators achieving a genuine bulk-insulating state is an important research topic. Recently, the material system (Bi,Sb)$_{2}$(Te,Se)$_{3}$ (BSTS) has been proposed as a topological insulator with high resistivity and a low carrier ... More
Interstellar X-ray Absorption Spectroscopy of Oxygen, Neon, and Iron with the Chandra LETGS Spectrum of X0614+091Aug 22 2000We find resolved interstellar O K, Ne K, and Fe L absorption spectra in the Chandra Low Energy Transmission Grating Spectrometer spectrum of the low mass X-ray binary X0614+091. We measure the column densities in O and Ne, and find direct spectroscopic ... More
SDSS-RASS: Next Generation of Cluster-Finding AlgorithmsNov 30 2000We outline here the next generation of cluster-finding algorithms. We show how advances in Computer Science and Statistics have helped develop robust, fast algorithms for finding clusters of galaxies in large multi-dimensional astronomical databases like ... More
A Catalog of Broad Absorption Line Quasars from the Sloan Digital Sky Survey Third Data ReleaseMar 03 2006Mar 03 2006We present a total of 4784 unique broad absorption line quasars from the Sloan Digital Sky Survey Third Data Release. An automated algorithm was used to match a continuum to each quasar and to identify regions of flux at least 10% below the continuum ... More
Boosting Transparency in Topological Josephson Junctions via Stencil LithographyNov 05 2017Oct 20 2018Hybrid devices comprised of topological insulator (TI) nanostructures in proximity to s-wave superconductors (SC) are expected to pave the way towards topological quantum computation. Fabrication under ultra-high vacuum conditions is necessary to attain ... More
The Environmental Dependence of Galaxy Properties in the Local Universe: Dependence on Luminosity, Local Density, and System RichnessNov 05 2004We investigate the environmental dependence of star formation and the morphology of galaxies in the local universe based on a volume-limited sample (0.030<z<0.065 and M_r<M_r^*+2) constructed from the data of the Sloan Digital Sky Survey. First, we focus ... More
Insights into teaching quantum mechanics in secondary and lower undergraduate educationJan 05 2017Feb 17 2017This study presents a review of the current state of research on teaching quantum mechanics in secondary and lower undergraduate education. A conceptual approach to quantum mechanics is being implemented in more and more introductory physics courses around ... More
No Pulsar Left Behind. I. Timing, Pulse-sequence Polarimetry, and Emission Morphology for 12 pulsarsOct 31 2017In this paper we study a set of twelve pulsars that previously had not been characterized. Our timing shows that eleven of them are "normal" isolated pulsars, with rotation periods between 0.22 and 2.65 s, characteristic ages between 0.25 Myr and 0.63 ... More
Preliminary Parallaxes of 40 L and T Dwarfs from the U.S. Naval Observatory Infrared Astrometry ProgramFeb 11 2004We present preliminary trigonometric parallaxes and proper motions for 22 L dwarfs and 18 T dwarfs measured using the ASTROCAM infrared imager. Relative to absolute parallax corrections are made by employing 2MASS and/or SDSS photometry for reference ... More
Stellar Coronae with \textit{XMM-Newton} RGS. I. Coronal StructureNov 30 2000First results from high-resolution coronal spectroscopy with the {\it XMM-Newton} Reflection Grating Spectrometers (RGS) are reviewed. Five stellar systems (HR 1099, Capella, Procyon, YY Gem, AB Dor) have been observed. The emphasis of the present paper ... More
Stellar Coronae with \textit{XMM-Newton} RGS. II. X-ray VariabilityNov 30 2000First results from high-resolution coronal spectroscopy of flares with the Reflection Grating Spectrometers on board the \textit{XMM-Newton} satellite are reviewed. Rotational modulation in the X-ray light curve of HR 1099 is discussed. Results from time-dependent ... More
Defect engineering in oxide heterostructures by enhanced oxygen surface exchangeAug 11 2010Jun 11 2013The synthesis of materials with well-controlled composition and structure improves our understanding of their intrinsic electrical transport properties. Recent developments in atomically controlled growth have been shown to be crucial in enabling the ... More