UScholar Works
 
Filters: Department: "Physics" Collection: "ir_uspace"
126 - 150 of 924
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CreatorTitleDescriptionSubjectDate
126 Rogachev, AndreySuperconducting properties of polycrystalline Nb nanowires templated by carbon nanotubesContinuous Nb wires, 7-15 nm in diameter, have been fabricated by sputter-coating single fluorinated carbon nanotubes. Transmission electron microscopy revealed that the wires are polycrystalline, having grain sizes of about 5 nm. The critical current of wires thicker than ~12 nm is very high (107 A...Polycrystalline Nb; Carbon nanotubes; Langer-Ambegaokar-McCumber-Halperin; Phase slips2003
127 Vardeny, Zeev ValentineEvidence for excimer photoexcitations in an ordered ?-conjugated polymer filmWe report pressure-dependent transient picosecond and continuous-wave photomodulation studies of disordered and ordered films of 2-methoxy-5-(2-ethylhexyloxy) poly(para-phenylenevinylene). Photoinduced absorption (PA) bands in the disordered film exhibit very weak pressure dependence and are assign...2011
128 Vardeny, Zeev ValentineSpectral analysis of near threshold random lasersEmission spectra from random lasing systems typically have numerous narrow resonant lines. When excited very near to the laser threshold there are fewer resonant lines which clarify the emission spectrum analysis. We studied three different random lasing systems including ?-conjugated polymer films...2012
129 DeTar, CarletonLight hadron spectrum - MILC results with the Kogut-Susskind and Wilson actions*We present the current status of our ongoing calculations of the light hadron spectrum with both Kogut-Susskind (KS) and Wilson quarks in the valence or quenched approximation. We discuss KS quarks first and find that the chiral extrapolation is potentially the biggest source of systematic error. F...Staggered quarks; Hadron spectrum; Kogut-Susskind quarks; Wilson quarks; Chiral extrapolation1998-01
130 Wu, Yong-ShiQuantum group, Bethe ansatz equations, and Bloch wave functions in magnetic fieldsThe wave functions for a two-dimensional Bloch electron in uniform magnetic fields at the mid-band points are studied by exploiting a connection to the quantum group Uq(sl2): A linear combination of its generators gives the Hamiltonian. We apply both analytic and numerical methods to obtain and an...Bloch electron1996-04
131 Lupton, John MarkIntrinsic room-temperature electrophosphorescence from a π-conjugated polymerElectrically induced phosphorescence from a poly(para-phenylene) ladder-type polymer is observed for the first time and characterized using time resolved spectroscopy. Short-lived phosphorescence is also observed in gated fluorescence spectra and is found to be quenched reversibly by oxygen. Therm...pi-conjugated polymers; Electrophosphorescence; Ladder-type polymer; Gated fluorescence spectra2002-09
132 Boehme, ChristophTriplet recombination at Pb centers and its implications for capture cross sectionsPulsed electrically detected magnetic resonance measurements are presented showing that Pb centers at the crystalline silicon (c-Sid) (111) to silicon dioxide sSiO2d interface can cause recombination of strongly coupled spin pairs in singlet and triplet configurations. The implication of these find...Silicon interfaces2005
133 Lupton, John MarkBragg scattering from periodically microstructured light emitting diodesWe present a simple method of generating a periodic wavelength scale structure in the optically active layer of a light emitting diode. This is achieved by solution deposition of a light emitting polymer on top of a corrugated substrate. The periodic structure allows waveguide modes normally trapped...Bragg scattering; Periodic wavelength scale structure2000
134 Vardeny, Zeev ValentineTransient-photomodulation-spectroscopy studies of carrier thermalization and recombination in α-Si:HThe transient response of mid-gap absorption in a-Si:H to pulsed optical excitation is studied as a function of time (300 ns to 30 ms) and sample temperature (10-220 K) with use of probe wavelengths ranging from 0.75 to 5.5 fim. A numerical inversion process applied to the data gives the distributio...Amorphous silicon; a-Si:H; Transient-photomodulation-spectroscopy; Carrier thermalization; Carrier recombination; Pulsed optical excitation1988-07
135 Gondolo, PaoloIndirect detection of dark matter in km-size neutrino telescopesNeutrino telescopes of kilometer size are currently being planned. They will be two or three orders of magnitude bigger than presently operating detectors, but they will have a much higher muon energy threshold. We discuss the trade-off between area and energy threshold for indirect detection of neu...Neutrino telescopes; Energy threshold; Neutralino annihilations; Supersymmetric models1998-11
136 Lupton, John MarkDevice model for polymer light emitting diodes: effect of temperature and oxidationWe present a temperature-dependent single carrier device model for polymer light-emitting diodes. The model includes both the injection of charge carriers over a barrier and the transport of charges across the device. To test the model, the temperature dependence of an LED based on the conjugated po...Single carrier; Temperature dependent; Poly(phenylene vinylene); Transport measurements; ITO; Disorder1999
137 Vardeny, Zeev ValentinePhotoresponse and electroresponse of polymers light emitting diodesWe have studied the photoresponse and electroresponse of light emitting diodes (LEDs ) made from a variety of soluble conducting polymers sandwiched between indium tin oxide (ITO) and metals including calcium, aluminum and copper. Under illumination all freshly prepared LEDs exhibit relatively large...Photoresponse; Electroresponse; Photovoltage; I-V curves1995
138 Ailion, David CharlesNuclear double resonance: cross relaxation rates between two spin speciesA rotating-frame nuclear-double-resonance experiment is reported in which the cross-relaxation rates between 7Li and 6Li in powdered lithium metal were measured. The theory developed my McArthur, Hahn, and Walstedt (MHW) is applied to these data and good agreement is obtained. We also apply this t...Nuclear-double-resonance; Lithium; MHW; Cross-relaxation1977
139 Saam, BrianUniversal long-time behavior of nuclear spin decays in a solidMagnetic resonance studies of nuclear spins in solids are exceptionally well suited to probe the limits of statistical physics. We report experimental results indicating that isolated macroscopic systems of interacting nuclear spins possess the following fundamental property: spin decays that start ...Nuclear spin decays; Hyperpolarized solid xenon; Chaos2008-08
140 Boehme, ChristophSpin-dependent processes at the crystalline Si-SiO2 interface at high magnetic fieldsAn experimental study on the nature of spin-dependent excess charge-carrier transitions at the interface between (111)-oriented phosphorous-doped ([P]) ~ 1015 cm−3) crystalline silicon and silicon dioxide at high magnetic field (B0~8.5 T) is presented. Electrically detected magnetic-resonance (E...Silicon interfaces; Spin-dependent recombination2008-07
141 Symko, Orest GeorgeObservation of a narrow pseudogap near the Fermi level of AlCuFe quasicrystalline thin filmsWe present the first experimental determination by tunneling spectroscopy of the density of states (DOS) close to the Fermi energy of AlCuFe quasicrystalline thin film samples. The measurements show that the Fermi level in a quasicrystal lies in a deep narrow pseudogap 60 m e V wide. Above an applie...AlCuFe; Quasicrystalline thin films; Pseudogap; Fermi level; Density of states; DOS1995-05
142 Boehme, ChristophUltra-sensitive electrical detection of spin Rabi oscillation at paramagnetic defectsA short review of the pulsed electrically detected magnetic resonance (pEDMR) experiment is presented. PEDMR allows the highly sensitive observation of coherent electron spin motion of charge carriers and defects in semiconductors by means of transient current measurements. The theoretical foundatio...Rabi oscillations; Electron spin resonance; Paramagnetic defects2006-04
143 Wu, Yong-ShiTowards a noncommutative geometric approach to matrix compactificationIn this paper we study generic M(atrix) theory compactifications that are specified by a set of quotient conditions. A procedure is proposed which both associates an algebra to each compactification and leads deductively to general solutions for the matrix variables. The notion of noncommutative g...Matrix theory; Compactification; Noncommutativity; Orbifolds; Orientifolds; Spacetime; Klein bottle; Gauge theory; Torus1998-07
144 Williams, Clayton C.Mapping of mobile charges on insulator surfaces with the electrostatic force microscopeMigration of surface ions in lateral fields on insulator surfaces may modify the electrical characteristics of underlying semiconductor structures causing device instabilities. A high sensitivity electrostatic force microscope is used to image the movement and spatial distribution of surface ions on...Insulator surfaces; Surface ions; Electrostatic force microscope1993
145 Vardeny, Zeev ValentinePhonon anomalies in Cu halidesA great number of the observed phonon anomalies in the zinc-blende phase of Cu-halide crystals are explained by means of a dynamical model. It is assumed that a Cu ion populates four equivalent off-center sites or its ideal position. The off-center Cu+ population is temperature and pressure dependen...Phonon anomalies; Cu-halide crystals; Cuprous halides1979-03
146 Sokolsky, PierreEvidence for correlated changes in the spectrum and composition of cosmic rays at extremely high energiesThe Utah Fly's Eye detector has revealed a change in the cosmic ray composition which is correlated with structure in the all-particle energy spectrum. The data can be fitted by a simple model of a steep power law spectrum of heavy nuclei which is overtaken at high energies by a flatter spectrum of ...Energy spectrum; Extensive air showers1993-11
147 Mishchenko, EugeneZero-bias anomaly in two-dimensional electron layers and multiwall nanotubesThe zero-bias anomaly in the dependence of the tunneling density of states n (e) on the energy e of the tunneling particle for two- and one-dimensional multilayered structures is studied. We show that for a ballistic two-dimensional (2D) system the first-order interaction correction to density of s...Spin-orbit coupling; Coulomb interaction2002-05
148 DeTar, CarletonLight quark spectrum with improved gauge and fermion actionsWe report on a study of the light quark spectrum using an improved gauge action and both Kogut-Susskind and Naik quark actions. We have studied six different lattice spacings, corresponding to plaquette couplings ranging from 6.8 to 7.9, with five to six quark masses per coupling. We compare the t...Quark spectrum; Kogut-Susskind quarks; Naik quarks1998-04
149 Wu, Yong-ShiQuantum phase transition in a multicomponent Bose-Einstein condensate in optical latticesWe present a general lattice model for a multicomponent atomic Bose-Einstein system in an optical lattice. Using the model, we analytically study the quantum phase transition between the Mott insulator and a superfluid. A mean-field theory is developed from the Mott-insulator ground state. When the...Quantum phase transitions; Optical lattices; Bose-Einstein condensation; Boson-Hubbard model; Superfluids2003-01
150 Symko, Orest GeorgeTemperature dependence of the order parameter in a dilute AgMn spin glassThe magnetization of a dilute AgMn spin glass containing 150 ppm Mn has been measured over the temperature range from 20 mK to 2 K in an applied field of 0.9 Oe, using a SQUID magnetometer. A comparison of the measured magnetization with numerical calculations of the magnetization based on the Mean ...AgMn spin glass; Mean random field; MRF; Temperature dependence; Order parameter; RKKY interactions1982
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