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Condensed Matter papers — page 216

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Thermoelectric Effect in High-Tc Superconductors: the Role of Density of States Fluctuations
We study the effect of the density of states (DOS) fluctuations on the thermoelectric coefficient of superconductor above critical temperature. It is shown that in the isotropic case it is the DOS…
D. V. Livanov, A. A. Varlamov, F. FedericiFeb 26, 1997
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Spectrum of boundary states in the open Hubbard chain
We use the Bethe Ansatz solution for the one dimensional Hubbard model with open boundary conditions and applied boundary fields to study the spectrum of bound states at the boundary. Depending on…
Gerald Bedürftig, Holger FrahmFeb 26, 1997
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Polaron effective mass from Monte Carlo simulations
A new Monte Carlo algorithm for calculating polaron effective mass is proposed. It is based on the path-integral representation of a partial partition function with fixed total quasi-momentum. Phonon…
P. E. Kornilovitch, E. R. PikeFeb 26, 1997
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Anomalous Drude Model
A generalization of the Drude model is studied. On the one hand, the free motion of the particles is allowed to be sub- or superdiffusive; on the other hand, the distribution of the time delay…
Hermann Schulz-BaldesFeb 26, 1997
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Low-Temperature Scaling Regime of Random Ferromagnetic-Antiferromagnetic Spin Chains
Using the Continuous Time Quantum Monte Carlo Loop algorithm, we calculate the temperature dependence of the uniform susceptibility, and the specific heat of a spin-1/2 chain with random…
Beat Frischmuth, Manfred SigristFeb 25, 1997
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Cooper pairs as low-energy excitations in the normal state
We discuss the normal state of a fermionic system in an idealized PSEUDOGAP REGIME, kB Tc < kB T << |Δ| << EF. Stable Cooper pairs induce a pseudogap of width |Δ| in the fermion energy…
O. Tchernyshyov, Y. J. UemuraFeb 22, 1997
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Spatiotemporal Stochastic Resonance in the Swift-Hohenberg Equation
We show the appearance of spatiotemporal stochastic resonance in the Swift-Hohenberg equation. This phenomenon emerges when a control parameter varies periodically in time around the bifurcation…
J. M. G. Vilar, J. M. RubíFeb 22, 1997
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Haldane and dimer gap in general double spin-chain models
We have obtained an analytic expression for the k dependence of excitation energy gap for an arbitrary double S=1/2 spin-chain by using the nonlocal unitary transformation and the variational…
Tota Nakamura, Satoshi Takada, Kiyomi Okamoto et al.Feb 20, 1997
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Nearly Antiferromagnetic Fermi Liquids: A Progress Report
I describe recent theoretical and experimental progress in understanding the physical properties of the two dimensional nearly antiferromagnetic Fermi liquids (NAFL's) found in the normal state…
David PinesFeb 20, 1997
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Fragmentation Phase Transition in Atomic Clusters II - Coulomb Explosion of Metal Clusters -
We discuss the role and the treatment of polarization effects in many-body systems of charged conducting clusters and apply this to the statistical fragmentation of Na-clusters. We see a first order…
O. Schapiro, P. J. Kuntz, K. Möhring et al.Feb 20, 1997
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Nonlinear optical response in higher fullerenes
Nonlinear optical properties of extracted higher fullerenes - C70, C76, C78, and C84 - are theoretically investigated. Magnitudes of off-resonant third-harmonic-generation are calculated by the…
K. HarigayaFeb 20, 1997
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Anomalous magnetophotoluminescence as a result of level repulsion in arrays of quantum dots
Selectively excited photoluminescence (SPL) of an array of self-organized In0.5Ga0.5As quantum dots has been measured in a magnetic field up to 11T. Anomalous magnetic field sensitivity of…
E. V. Tsiper, P. D. Wang, J. L. Merz et al.Feb 19, 1997
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Direct Mott Insulator-to-Superfluid Transition in the Presence of Disorder
We introduce a new renormalization group theory to examine the quantum phase transitions upon exiting the insulating phase of a disordered, strongly interacting boson system. For weak disorder we…
Ferenc Pazmandi, Gergely T. ZimanyiFeb 19, 1997
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Diagrammatic Method for Wide Correlators in Gaussian Orthogonal and Symplectic Random Matrix Ensembles
We calculate connected correlators in time dependent Gaussian orthogonal and symplectic random matrix ensembles by a diagrammatic method. We obtain averaged one-point Green's functions in the…
Chigak Itoi, Yoshinori SakamotoFeb 18, 1997
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Comment on "Continuum dual theory of the transition in 3D lattice superconductor"
A recent paper by Herbut in J. Phys. A: Math. Gen. 29, 1 (1996) is shown to contain an internal inconsistency which invalidates the principal conclusion of the paper that the magnetic…
Hagen Kleinert, Adriaan M. J. SchakelFeb 18, 1997
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Scaling Properties of Antiferromagnetic Transition in Coupled Spin Ladder Systems Doped with Nonmagnetic Impurities
We study effects of interladder coupling on critical magnetic properties of spin ladder systems doped with small concentrations of nonmagnetic impurities, using the scaling theory together with…
Masatoshi Imada, Youichirou IinoFeb 18, 1997
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Contrasts between coarsening and relaxational dynamics of surfaces
We discuss static and dynamic fluctuations of domain walls separating areas of constant but different slopes in steady-state configurations of crystalline surfaces both by an analytic treatment of…
Martin Siegert, Michael Plischke, Royce K. P. ZiaFeb 17, 1997
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Localization in a rough billiard: A sigma model formulation
We consider the quantum dynamics of a particle in a weakly rough billiard. The Floquet operator for reflection at the boundary is obtained as a unitary band matrix. The resulting dynamics in angular…
Klaus M. FrahmFeb 15, 1997
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Sine-Gordon mean field theory of a Coulomb Gas
Sine-Gordon field theory is used to investigate the phase diagram of a neutral Coulomb gas. A variational mean field free energy is constructed and the corresponding phase diagrams in two (2d) and…
Alexandre Diehl, Marcia C. Barbosa, Yan LevinFeb 14, 1997
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Emergence of Quantum Ergodicity in Rough Billiards
By analytical mapping of the eigenvalue problem in rough billiards on to a band random matrix model a new regime of Wigner ergodicity is found. There the eigenstates are extended over the whole…
Klaus M. Frahm, Dima L. ShepelyanskyFeb 14, 1997
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Gapless spectrum in a class of S=1 exchange models with long-range interactions
We present evidence for the absence of a gap in a class of S=1 antiferromagnetic exchange models. The spin exchange is long-ranged of the type -(-1)i-j/|i-j|α where 1<α<3. We have shown…
P. D. Sacramento, V. R. VieiraFeb 13, 1997
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A New Family of Integrable Extended Multi-band Hubbard Hamiltonians
We consider exactly solvable 1d multi-band fermionic Hamiltonians, which have affine quantum group symmetry for all values of the deformation. The simplest Hamiltonian is a multi-band t-J model with…
J. Ambjorn, A. Avakyan, T. Hakobyan et al.Feb 13, 1997
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Intermediate Valence Model for Tl2Mn2O7
There have been speculations about the need to find a new mechanism to explain the colossal magnetoresistance exhibited by this material, having pyrochlore structure and thus differing structurally…
C. I. Ventura, B. R. AlascioFeb 13, 1997
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Kondo Effect in High-Tc Cuprates
We study the Kondo effect due to the nonmagnetic impurity, e.g., Zn, in high-Tc cuprates based on the spin-change separated state. In the optimal or overdoped case with the Kondo screening, the…
Naoto Nagaosa, Patrick A. LeeFeb 12, 1997
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Observation of the logarithmic dispersion of high frequency edge excitations
We report phase sensitive measurements of microwave propagation through a high mobility two dimensional electron gas subjected to a perpendicular magnetic field. Two types of configurations were…
N. Q. Balaban, U. Meirav, Hadas Shtrikman et al.Feb 12, 1997
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