Tuning the spin Hamiltonian of NENP by external pressure: a neutron scattering studyWe report an inelastic neutron scattering study of antiferromagnetic spin dynamics in the Haldane chain compound Ni(C2H8N2)2NO2ClO4 (NENP) under external hydrostatic pressure P = 2.5 GPa. At ambient…I. A. Zaliznyak, D. C. Dender, C. Broholm et al.·Sep 12, 1997SaveLearn
Theory of hole propagation in one dimensional insulators and superconductorsThe dynamical properties of hole motion in an antiferromagnetic background are determined in one dimensional models in zero magnetic field, where spin isotropy holds, as well as in an external…S. Sorella, A. Parola·Sep 12, 1997SaveLearn
Nonequilibrium Noise in Metals at Mesoscopic ScalesWe review a semiclassical theory of high-field noise in degenerate conductors, based on propagator solutions to the Boltzmann equation for the fluctuation distribution function. The theory provides a…F. Green, M. P. Das·Sep 12, 1997SaveLearn
Metal-Insulator Transition in Disordered and Interacting SystemsThis paper is being withdrawn.Sanjoy K. Sarker·Sep 11, 1997SaveLearn
Finite-size scaling properties and Casimir forces in an exactly solvable quantum statistical-mechanical modelA d-dimensional finite quantum model system confined to a general hypercubical geometry with linear spatial size L and ``temporal size'' 1/T (T - temperature of the system) is considered in…H. Chamati, D. M. Danchev, N. S. Tonchev·Sep 10, 1997SaveLearn
Quantized Vortices in Superfluids and SuperconductorsWe give a general review of recent developments in the theory of vortices in superfluids and superconductors, discussing why the dynamics of vortices is important, and why some key results are still…D. J. Thouless, Ping Ao, Qian Niu et al.·Sep 10, 1997SaveLearn
Phase Separation Kinetics in a Model with Order-Parameter Dependent MobilityWe present extensive results from 2-dimensional simulations of phase separation kinetics in a model with order-parameter dependent mobility. We find that the time-dependent structure factor exhibits…Sanjay Puri, Alan Bray, Joel Lebowitz·Sep 10, 1997SaveLearn
Specific Heat of defects in the Haldane System Y2BaNiO5We calculate the specific heat of the antiferromagnetic spin-1 chain compound Y2BaNi1-xZnxO5 in the presence of a magnetic field. The low-energy spectrum of a Heisenberg Hamiltonian, which…K. Hallberg, C. D. Batista, A. A. Aligia·Sep 9, 1997SaveLearn
Is the direct observation of electronic coherence in electron transfer reactions possible?The observability of electronic coherence in electron transfer reactions is discussed. We show that under appropriate circumstances large-amplitude oscillations can be found in the electronic…A. Lucke, C. H. Mak, R. Egger et al.·Sep 9, 1997SaveLearn
Exact zero-point energy shift in the e (n~E), t (n~H) many modes dynamic Jahn-Teller systems at strong couplingWe find the exact semiclassical (strong coupling) zero-point energy shifts applicable to the e (n E) and t (n H) dynamic Jahn-Teller problems, for an arbitrary number n of…Nicola Manini, Erio Tosatti·Sep 8, 1997SaveLearn
Band Crossing and Novel Low-Energy Behaviour in a Mean Field Theory of a Three-Band Model on a Cu--O latticeWe study correlation effects in a three-band extended Hubbard model of Cu -- O planes within the 1/N mean field approach, in the infinite U limit. We investigate the emerging phase diagram and…D. I. Golosov, A. E. Ruckenstein, M. L. Horbach·Sep 8, 1997SaveLearn
Berry-Phase and Symmetry of the Ground State in Dynamical Jahn-Teller SystemsWe show through selected examples, relevant to the physics of fullerene ions, that the presence of a Berry phase in dynamical Jahn-Teller systems does not guarantee the degeneracy of the ground…Paolo De Los Rios, Nicola Manini·Sep 8, 1997SaveLearn
Behavior of excitonic levels in symmetric and asymmetric double quantum wells in a magnetic fieldWe studied theoretically the excitonic energy levels and the optical absorption spectra for double quantum wells, both symmetric and asymmetric, in the presece of an homogeneous magnetic field.…Francisco Vera, Zdenka Barticevic·Sep 8, 1997SaveLearn
Unpolarized quasielectrons and the spin polarization at filling fractions between 1/3 and 2/5We prove that for a hard core interaction the ground state spin polarization in the low Zeeman energy limit is given by P=2/ν-5 for filling fractions in the range 1/3 ≤ν≤ 2/5 . The same…Jacek Dziarmaga, Meik Hellmund·Sep 8, 1997SaveLearn
Metal-Insulator Transition in the Two-Dimensional Hubbard Model at Half-Filling with Lifetime Effects within the Moment ApproachWe explore the effect of the imaginary part of the self-energy, ImΣ(k,ω), having a single pole, Ω(k,ω), with spectral weight, α(k), and quasi-particle lifetime, Γ(k),…J. J. Rodríguez-Núñez, S. Schafroth·Sep 5, 1997SaveLearn
A Study of Bose-Einstein Condensation in a Two-Dimensional Trapped GasWe examine the possibility of Bose-Einstein condensation (BEC) in two-dimensional (2D) system of interacting particles in a trap. We use a self-consistent mean-field theory of Bose particles…William J. Mullin·Sep 5, 1997SaveLearn
Classical double-layer atoms: artificial moleculesThe groundstate configuration and the eigenmodes of two parallel two-dimensional classical atoms are obtained as function of the inter-atomic distance (d). The classical particles are confined by…B. Partoens, V. A. Schweigert, F. M. Peeters·Sep 5, 1997SaveLearn
Magnetic Dipole Absorption of Radiation in Small Conducting ParticlesWe give a theoretical treatment of magnetic dipole absorption of electromagnetic radiation in small conducting particles, at photon energies which are large compared to the single particle level…M. Wilkinson, B. Mehlig, P. N. Walker·Sep 5, 1997SaveLearn
Unifying the Phase Diagrams of the Magnetic and Transport Properties of La(2-x)SrxCuO4, 0 < x < 0.05An extensive experimental and theoretical effort has led to a largely complete mapping of the magnetic phase diagram of La(2-x)SrxCuO4, and a microscopic model of the spin textures produced in the…E. Lai, R. J. Gooding·Sep 5, 1997SaveLearn
Exchange-Correlation Hole in Polarized Insulators: Implications for the Microscopic Functional Theory of DielectricsWe present a simple and direct proof that the exchange-correlation hole, and therefore the exchange-correlation energy, in a polarized insulator is not determined by the bulk density alone. It is…Gerardo Ortiz, Ivo Souza, Richard M. Martin·Sep 5, 1997SaveLearn
Avoided Band Crossings: Tuning Metal-Insulator Transitions in Chaotic SystemsWe show that avoided crossings of energy bands may give rise to a variety of phenomena such as transitions from metal to insulator and vice versa, changes in localization lengths, and changes in the…R. Ketzmerick, K. Kruse, T. Geisel·Sep 4, 1997SaveLearn
DC motion of ac driven sine-Gordon solitonsWe investigate the possibility of dc soliton motion sustained by pure ac driving in the sine-Gordon model. We show by means of the collective coordinate formalism that ac driving induces a net dc…Niurka R. Quintero, Angel Sánchez·Sep 4, 1997SaveLearn
Suppression of antiferromagnetic correlations by dipole-type impurities in lamellar cupratesIn doped lamellar cuprates, localized holes create ferromagnetic bonds and cause spin canting similar to that caused by magnetic dipoles. At low temperatures, these dipoles are frozen, behaving like…I. Ya. Korenblit, V. Cherepanov, Amnon Aharony et al.·Sep 4, 1997SaveLearn
Low Temperature Viscosity in Elongated FerrofluidsWe have studied the relaxation and transport properties of a ferrofluid in an elongational flow. These properties are influenced by the bistable nature of the potential energy. Bistability comes from…T. Alarcon, A. Perez-Madrid, J. M. Rubi·Sep 4, 1997SaveLearn
Geometrical Properties of Cumulant ExpansionsCumulants represent a natural language for expressing macroscopic properties of a solid. We show that cumulants are subject to a nontrivial geometry. This geometry provides an intuitive understanding…K. Kladko, P. Fulde·Sep 4, 1997SaveLearn