G. Blatter

Vortex dynamics and the Hall anomaly: A microscopic analysis.

We present a microscopic derivation of the equation of motion for a vortex in a superconductor. A coherent view on vortex dynamics is obtained, in which {\it both} hydrodynamics {\it and} the vortex core contribute to the forces acting on a vortex. The competition between these two provides an interpretation of the observed sign change in the Hall angle in superconductors with mean free path

Strong Pinning and Plastic Deformations of the Vortex Lattice.

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Superfluidity versus Bloch Oscillations in Confined Atomic Gases

of the order of the coherence length

Analysis of the low field critical state in ceramic high-Tc superconductors

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(4+N)-Dimensional Elastic Manifolds in Random Media: A Renormalization-Group Analysis

in terms of broken particle-hole symmetry, which is related to details of the microscopic mechanism of superconductivity.

Quantum computing with superconducting phase qubits

We investigate numerically the dynamically generated plastic deformations of a 3D vortex lattice driven through a disorder potential with isolated, strong pinning centers (pointlike or extended along the field direction). We find that the vortex lattice exhibits a very peculiar dynamical behavior in the plastic flow regime, in particular, topological excitations consisting of three or four entangled vortices are formed. We determine the critical current density {ital j}{sub {ital c}} and the activation energy for depinning {ital U}{sub {ital c}} in the presence of a finite density of strong pinning centers. {copyright} {ital 1996 The American Physical Society.}

Vortex entanglement and broken symmetry.

We study the superfluid properties of (quasi) one-dimensional bosonic atom gases/liquids in traps with finite geometries in the presence of strong quantum fluctuations. Driving the condensate with a moving defect we find the nucleation rate for phase slips using instanton techniques. While phase slips are quenched in a ring resulting in a superfluid response, they proliferate in a tube geometry where we find Bloch oscillations in the chemical potential. These Bloch oscillations describe the individual tunneling of atoms through the defect and thus are a consequence of particle quantization.

Quantum collective creep in anisotropic superconductors

Abstract Results of magnetization measurements on polycrystalline YBa2Cu3O7−δ samples at very low fields (below 10 Oe) are presented. Using the critical state model we are able to deduce the “true” zero field critical current density which in transport measurements is masked by self-field effects. Our method is useful to test the material quality obtained by different sintering methods. Our analysis does not rely on a particular form of the critical state model; we rather show that the various versions used in the literature are in close quantitative agreement in the low field limit.

Vortices in high temperature superconductors: the statistical mechanics and dynamics of strings

Motivated by the problem of weak collective pinning of vortex lattices in hightemperature superconductors, we study the model system of a four-dimensional elastic manifold with N transverse degrees of freedom (4+N-model) in a quenched disorder environment. We assume the disorder to be weak and short-range correlated, and neglect thermal effects. Using a real-space functional renormalization group (FRG) approach, we derive a RG equation for the pinning-energy correlator up to two-loop correction. The solution of this equation allows us to calculate the size Rc of collectively pinned elastic domains as well as the critical force Fc, i.e., the smallest external force needed to drive these domains. We find Rc ∝ � � 2 p exp(�1/�p) and Fc ∝ � 2�2 p exp(−2�1/�p), �

Quantum Nucleation of Phase Slips in Bose—Einstein Condensates

Abstract The superconducting phase qubit combines Josephson junctions into superconducting loops and defines one of the promising solid state device implementations for quantum computing. Here, we propose two hardware realizations for superconducting phase qubits, where the first is based on 2 φ -periodic s-wave–d-wave–s-wave Josephson junctions, while the second proposal involves five Josephson junctions arranged in a loop which is frustrated by a π-junction, a Josephson junction with a ground state characterized by a π -phase shift across.