arXiv subjects

Peter Olsson

Publications and source records attributed to Peter Olsson.

42 records · Page 3Linked to original sources

arXiv1999

High-Tc Superconductors in Applied Magnetic Fields Parallel to the CuO Planes: First Order Transition with Slow Onset of Resistivity

The three dimensional uniformly frustrated XY model is used as a model of a high temperature superconductor in an applied magnetic field parallel to the CuO-planes. Through Monte Carlo simulations with anisotropy $η^2 = 10$ on large lattices we find evidence for a first order transition. Earlier simulations and theoretical treatments are discussed and the experimentally found smooth onset of resistivity is suggested to be due to a large potential barrier against vortex line motion above $T_c$ present for perfect alignment of the applied field.

cond-mat↗

arXiv1999

Vortex dynamics for two-dimensional XY models

Two-dimensional XY models with resistively shunted junction (RSJ) dynamics and time dependent Ginzburg-Landau (TDGL) dynamics are simulated and it is verified that the vortex response is well described by the Minnhagen phenomenology for both types of dynamics. Evidence is presented supporting that the dynamical critical exponent $z$ in the low-temperature phase is given by the scaling prediction (expressed in terms of the Coulomb gas temperature $T^{CG}$ and the vortex renormalization given by the dielectric constant $\tildeε$) $z=1/\tildeεT^{CG}-2\geq 2$ both for RSJ and TDGL and that the nonlinear IV exponent a is given by a=z+1 in the low-temperature phase. The results are discussed and compared with the results of other recent papers and the importance of the boundary conditions is emphasized.

cond-mat.supr-con↗

arXiv1999

Correlation Lengths in the Vortex Line Liquid of a High Tc Superconductor

We use the three dimensional uniformly frustrated XY model, as a model for a high temperature superconductor in an applied magnetic field, to explicitly measure the longitudinal correlation length xi_z in the vortex line liquid phase. We determine the scaling of xi_z with magnetic field and system anisotropy close to the vortex lattice melting transition. We apply our results to determine the extent of longitudinal correlations in YBCO just above melting.

cond-mat.supr-con↗

arXiv1997

Critical Behavior of the Meissner Transition in the Lattice London Superconductor

We carry out Monte Carlo simulations of the three dimensional (3D) lattice London superconductor in zero applied magnetic field, making a detailed finite size scaling analysis of the Meissner transition. We find that the magnetic penetration length λ, and the correlation length ξ, scale as λ~ ξ~ |t|^{-ν}, with ν= 0.66 \pm 0.03, consistent with ordinary 3D XY universality, ν_XY ~ 2/3. Our results confirm the anomalous scaling dimension of magnetic field correlations at T_c.

cond-mat.supr-con↗

arXiv1996

Monte Carlo study of the Villain version of the fully frustrated XY model

The fully frustrated XY model with Villain interaction on a square lattice is studied by means of Monte Carlo simulations. On the basis of the universal jump condition it is argued that there are two distinct transitions in the model, corresponding to the loss of XY order and Z_2 order, respectively. The Kosterlitz-Thouless (KT) transition is analyzed by finite size scaling of the helicity modulus at lattices of size L = 32 through 128, giving T_KT = 0.8108(1). The vorticity-vorticity correlation function is used to determine two different characteristic lengths, the Z_2 correlation length ξ, and the screening length λ, associated with the KT transition and free vortices. The temperature dependence of ξis examined in order to determine T_c and the correlation length exponent, ν. The exponent is found to be consistent with the 2D Ising value, ν= 1, and the obtained critical temperature is T_c = 0.8225(5). The determinations of both ξand νare done carefully, first applying the techniques to the 2D Ising model, which serves as a convenient testing ground.

cond-mat↗

arXiv1995

Two phase transitions in the fully frustrated $XY$ model

The fully frustrated $XY$ model on a square lattice is studied by means of Monte Carlo simulations. A Kosterlitz-Thouless transition is found at $T_{\rm KT} \approx 0.446$, followed by an ordinary Ising transition at a slightly higher temperature, $T_c \approx 0.452$. The non-Ising exponents reported by others, are explained as a failure of finite size scaling due to the screening length associated with the nearby Kosterlitz-Thouless transition.

cond-mat↗