UScholar Works
 
Filters: Department: "Physics" Collection: "ir_uspace"
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CreatorTitleDescriptionSubjectDate
1 Vardeny, Zeev Valentine; Ehrenfreund, Eitan A.Illumination-induced metastable polaron-supporting state in poly(p-phenylene vinylene) filmsWe found an illumination-induced metastable polaron-supporting state in films of a soluble derivative of poly-p-phenylene vinylene (MEH-PPV). Pristine, nonilluminated MEH-PPV polymer films do not show longlived photogenerated polarons. Prolonged UV illumination, however, is found to induce a revers...Metastable polaron-supporting state; Poly(p-phenylene vinylene); PPV; MEH-PPV; Excitons2007-07
2 Symko, Orest GeorgeMicrowave absorption in the superconducting and normal phases of Y-Ba-Cu-OMicrowave absorption in a dc magnetic field up to 12 kG, attributed to nonequilibrium contributions to the ac susceptibility, appears at Tc as the sample is cooled. ESR measurements of YBa-Cu-O show that Cu2+ exists only in the fraction of the sample which is not superconducting in a distorted octa...Microwave absorption; Superconducting phase; YBCO; High Tc1987-08
3 Mishchenko, EugeneCoulomb drag by small momentum transfer between quantum wiresWe demonstrate that in a wide range of temperatures Coulomb drag between two weakly coupled quantum wires is dominated by processes with a small interwire momentum transfer. Such processes, not accounted for in the conventional Luttinger liquid theory, cause drag only because the electron dispersion...Coulomb drag; Quantum wires; Luttinger liquid2003-09
4 Mattis, Daniel C.Existence of two phase transitions in Hubbard modelWe solve the Hubbard model, for one electron per atom in a simple cubic structure, using one-particle Green's functions. We determine the accuracy of this calculation to be good by comparison with an exact solution by Lieb and Wu of a one-dimensional limiting case.Critical temperature1969-12
5 Lupton, John MarkUltrafast intramolecular energy transfer in single conjugated polymer chains probed by polarized single chromophore spectroscopySingle molecule spectroscopy of rigid-rod ladder-type conjugated polymers reveals individual chromophore units on a polymer chain, exhibiting fluorescence linewidths of less than 1 nm. Whereas the fluorescence from a single chromophore is fully linearly polarized at low temperatures, a number of exc...Single molecule spectroscopy; Intramolecular energy transfer; Chromophore spectroscopy; Chromophores; Rigid-rod; Ladder-type2004
6 Williams, Clayton C.Single electron tunneling to insulator surfaces detected by electrostatic forceThe detection of single-electron tunneling events between a metallic scanning probe tip and an insulating surface is demonstrated by an electrostatic force method. When a voltage-biased oscillating atomic force microscopy tip is placed within tunneling range of the surface of an insulator, single...Single electron; Tunneling events; Scanning tunneling microscope2002
7 Vardeny, Zeev Valentine; Raikh, Mikhail E.Emission spectrum of a dipole in a semi-infinite periodic dielectric structure: effect of the boundaryThe emission spectrum of a dipole embedded in a semi-infinite photonic crystal is calculated. For simplicity we study the case in which the dielectric function is sinusoidally modulated only along the direction perpendicular to the boundary surface plane. In addition to oscillations of the emission...Emission spectrum; Dipole; Periodic dielectric structure2000-07
8 Lupton, John MarkProbing the electrode-polymer interface in conjugated polymer devices with surface-enhanced Raman scatteringA crucial consideration in organic devices is the role of the interface between a metal electrode and the active polymer material. Here, we use the conjugated polymer poly[2-methoxy-5-(2-ethylhexyl-oxy)-1,4-phenylene-vinylene] (MEH-PPV) with model gold and silver electrodes to perform surface-enhanc...2012-01-01
9 Mattis, Daniel C.Theory of ferromagnetism in carbon foamAn explanation is proposed for spontaneous magnetism in the material, "carbon nanofoam," in terms of random ferrimagnetism. Wherever a carbon nanotube branches out, an electron trap is created at the junction. Electrons occupying neighboring junctions align their spins antiparallel.Carbon foam; Nanotubes; Nanofoam2005-04
10 Ailion, David CharlesNMR determination of structural domains in NaCNMeasurements of the first- and second-order quadrupole energy-level shifts are performed in a 23Na NMR experiment in a single crystal of NaCN. Twelve orthorhombic domains are found below the phase transition at 15°C. They consist of six pairs of domains with each one oriented by an angle 2/3 rel...NMR; Nuclear magnetic resonance; Crystals; Structural domains1980
11 Mattis, Daniel C.Short-range versus long-range order in a model binary alloyWe calculate the free energy of a linear binary metallic alloy using an exact transfer-matrix formalism. We obtain for the first time the electronic band structure when there is nonvanishing short-range order and calculate the temperature dependence of the short-range order parameter. Following Foo...Binary alloys; Density of state; Free energy1971-07
12 Vardeny, Zeev Valentine; Raikh, Mikhail E.Mesoscopic cooperative emission from a disordered systemWe study theoretically the cooperative light emission from a system of N»1 classical oscillators confined within a volume with spatial scale L much smaller than the radiation wavelength λο=2rrc/ω0. We assume that the oscillator frequencies are randomly distributed around a central frequency ω...Mesoscopic cooperative emission; Disordered systems; Oscillators2000-05
13 Vardeny, Zeev ValentineSpecific heats and lattice dynamics of cuprous halidesThe specific heats Cp(T) of CuCl, CuBr, and Cul were measured by the adiabatic calorimetric technique. The corresponding Debye temperature for each crystal is given and a comparison between the results is drawn. The room-temperature phonon dispersion relations for these cystals are fitted by a nine...Cuprous halides; CuBr; CuCl; CuI1978-10
14 Lupton, John MarkUnraveling the inhomogeneously broadened absorption spectrum of conjugated polymers by single-molecule light-harvesting action spectroscopyThe distribution of chromophores in single polymer chains is revealed by photoluminescence excitation spectroscopy under excitation of the backbone and detection of emission from an end cap. Spectral broadening in excitation exceeds that in emission. An increase in vibronic coupling for shorter (h...Spectral broadening; Chromophores2009-10
15 Ailion, David CharlesNMR relaxation study of molecular motions between unequal potential wells in solid trans, trans- muconodinitrileWe report observations of extremely unusual proton NMR relaxation rates in solid trans, transmuconodinitrile (TMD, N=C-CH = CH-CH = CH-C = N). In particular we measured, over the temperature range 77-423 °K, proton dipolar relaxation times Tw and spin lattice relaxation times Tt (at 24 and 58 MH...NMR; Nuclear magnetic resonance; Lattices; Relaxation time1977
16 Mattis, Daniel C.Bond asymmetry and high-Tc superconductivityWe propose a simple mechanism, anchored in weak-coupling BCS theory, which ties together the following facts: high Tc; quasi two dimensionality; orthorhombic distortion and/or disordered lines of oxygen; proximity to a metal-insulator transition; and anomalously small isotope effects.Distortion; Singularity; Oxygen1987
17 Mishchenko, EugeneGeneration of spin current by Coulomb dragCoulomb drag between two quantum wires is exponentially sensitive to the mismatch of their electronic densities. The application of a magnetic field can compensate this mismatch for electrons of opposite spin directions in different wires. The resulting enhanced momentum transfer leads to the conv...Spin current; Coulomb drag; Quantum wires2006-12
18 Mattis, Daniel C.Three-band model of high-Tc superconductivityWe reduce the three-band model of planar CuO2 to a single-band of composite fermions. We obtain hopping parameters teff(Rij), repulsive potentials Ueff and V(Ri j), and the superexchange interactions J(Ri j) necessary for both antiferromagnetism and superconductivity. The ratios of these quantitie...Copper oxides; Composite fermions; Charge transport; Bloch energies; Superexchange1999-03
19 Mattis, Daniel C.Theory of superexchange in CuO2The limit method allows exact analysis of low-lying electronic states in a strong-coupling model Cu02 plane. We extend it to nonorthogonal orbitals and fit to a t-t'-J model. The superexchange parameter is J = g32t*, with the unit of energy and g3 a lumped parameter.Copper oxides; Superexchange1995-12
20 Vardeny, Zeev ValentineElectroabsorption spectroscopy of single walled nanotubesWe have measured the electric field modulated absorption of a sample of single-walled nanotubes (SWNT) suspended in a solid polyvinyl alcohol matrix. The electroabsorption (EA) spectrum roughly follows the first derivative of the absorption with respect to photon energy, scales quadratically with t...Electroabsorption spectroscopy; Single-walled nanotubes; SWNT2005
21 Wu, Yong-ShiGround-state degeneracy in the Levin-Wen model for topological phasesWe study the properties of topological phases by calculating the ground-state degeneracy (GSD) of the two-dimensional Levin-Wen (LW) model. Here it is explicitly shown that the GSD depends only on the spatial topology of the system. Then we show that the ground state on a sphere is always nondegener...2012-01-01
22 Dawson, KyleHigh-voltage-compatible fully depleted CCDsWe describe charge-coupled device (CCD) development activities at the Lawrence Berkeley National Laboratory (LBNL). Back-illuminated CCDs fabricated on 200-300 fxm thick, fully depleted, high-resistivity silicon substrates are produced in partnership with a commercial CCD foundry. The CCDs are full...Large Synoptic Survey Telescope; X-ray emission; XMM22352006
23 Mattis, Daniel C.Limit model of CuO2 planes: exact resultsWe solve the simplest tight-binding model of electrons in a CuO2 plane with Coulomb repulsion only on the copper ions, by a limiting procedure which retains all contributions 0(t2/U) while projecting out the higher order terms. In addition to the ground state energy we identify a variety of quasipar...Electrons; Particle-hole1995
24 Mattis, Daniel C.Second-order phase transition in a model random alloyWe investigate the existence and stability of long-range order in a simple model of a binary alloy. We find that for electron concentrations in the vicinity of one per atom, in bipartite lattices, long-range order of the atoms exists at low temperatures, and we find that the system undergoes a secon...Phase transition; Random alloys; Quasiparticles; Density of state1973-03
25 Vardeny, Zeev ValentinePhotogeneration and recombination processes of neutral and charged excitations in films of a ladder-type poly(para-phenylene)We introduce a version of the cw photomodulation technique, measured far from the steady state, for obtaining the quantum efficiency, η, of long-lived photoexcitations in p-conjugated polymers. We apply this technique to films of a ladder-type poly(para-phenylene) [mLPPP] for studying the photoge...Photogeneration; Recombination process; Neutral excitations; Charged excitations; Ladder-type poly(para-phenylene)1999-08
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