凝聚态物理
The nonequilibrium phase transition has been studied by Monte Carlo simulation in a ferromagnetically interacting (nearest neighbour) kinetic Ising model in presence of a sinusoidally oscillating magnetic field. The ('specific-heat')…
We report a quasi-exact power law behavior for Ising critical temperatures on hypercubes. It reads $J/k_BT_c=K_0[(1-1/d)(q-1)]^a$ where $K_0=0.6260356$, $a=0.8633747$, $d$ is the space dimension, $q$ the coordination number ($q=2d$), $J$…
The effects of a magnetic field on a modulated phase is studied. A modulated phase is found to have two critical fields $H_{1}$ and $H_{2}$. For a large enough magnetic field. $H_1$ can be approximated by a linear law. As a result, the…
We review transport measurements in a normal metal (N) in contact with one or two superconducting (S) islands. From the experiment, we distinguish the Josephson coupling, the mesoscopic fluctuations and the proximity effect. In a…
We investigate the Mott transition in infinite dimensions in the orbitally degenerate Hubbard model. We find that the qualitative features of the Mott transition found in the one band model are also present in the orbitally degenerate case.…
Large variations in stock prices happen with sufficient frequency to raise doubts about existing models, which all fail to account for non-Gaussian statistics. We construct simple models of a stock market, and argue that the large…
Motivated by recent experimental activities on surface critical phenomena, we present a detailed theoretical study of the near-surface behavior of the local order parameter m(z) in Ising-like spin systems. Special attention is paid to the…
Pure electronic Raman spectra with no phonon structures superimposed to the electronic continuum, are reported for the first time, in optimally doped $HgBa_{2}CaCu_{2}O_{6+\delta } $ single crystals $(T_{c }=126 $ K). Our low temperature…
We theoretically investigate the spatial dependence of the order parameter of the two-dimensional semi-infinite Ising model with a free surface at or above the bulk critical temperature. Special attention is paid to the influence of a…
In this last of three articles on the optical absorption of electrons in a half-filled Peierls-distorted chain we address the dimerized extended Hubbard model in the limit of a large on-site interaction $U$. When the Hubbard interaction is…
In this second of three articles on the optical absorption of electrons in a half-filled Peierls-distorted chain we present exact results for strongly correlated tight-binding electrons. In the limit of a strong on-site interaction $U$ we…
In this first of three articles on the optical absorption of electrons in half-filled Peierls-distorted chains we present analytical results for non-interacting tight-binding electrons. We carefully derive explicit expressions for the…
We present a semiclassical study of a transport process, the tunneling, in the presence of a magnetic field and a dissipative environment. We have found that the problem can be mapped onto an effective one-dimensional one, and the tunneling…
On the basis of the one--band t-t'-Hubbard model a self-consistent renormalization theory of magnetic short--range order (SRO) in the paramagnetic phase is presented combining the four-field slave-boson functional-integral scheme with the…
The problem of finding the minimum-energy configuration of particles on a lattice, subject to a generic short-ranged repulsive interaction, is studied analytically. The study is relevant to charge ordered states of interacting fermions, as…
Local percolation probabilities are used to characterize the connectivity in porous and heterogeneous media. Together with local porosity distributions they allow to predict transport properties \cite{hil91d}. While local porosity…
We study numerically the influence of the substrate (boundary conditions) on the finite--size scaling properties of the superfluid density $\rho_s$ in superfluid films of thickness $H$ within the XY model employing the Monte Carlo method.…
We discuss the experimental photoemission and inverse photoemission of early transition metal oxides, in the light of the dynamical mean field theory of correlated electrons which becomes exact in the limit of infinite dimensions. We argue…
The McMillan-Rowell tunneling inversion program, which extracts the electron-phonon spectral function $\alpha^2F(\Omega)$ and the Coulomb pseudopotential $\mu^*$ from experimental tunneling data, is generalized to include the lowest-order…
In this work, we study a continuous quantum system of a mixture of bosons and fermions with the supersymmetry SU(m|n). The particles are confined in a harmonic well and interact with each other through the 1/r2 interaction. The ground state…