Related papers: Vortex Line Fluctuations in Model High Temperature…
Order-disorder transitions take place in many physical systems, but observing them in detail in real materials is difficult. In two- or quasi-two-dimensional systems, the transition has been studied by computer simulations and…
We carry out simulations of a lattice London superconductor in a magnetic field B, with a finite magnetic penetration length \lambda. We find that superconducting coherence parallel to B persists into the vortex line liquid. We argue that…
Spontaneous nucleation and the consequent penetration of vortices into thin superconducting films and wires, subjected to a magnetic field, can be considered as a nonlinear stage of primary instability of the current-carrying…
The work reported in my doctoral thesis is an experimental study of vortex dynamics and phase transitions in thin films of type II superconductors using scanning tunneling spectroscopy, low frequency ac susceptibility measurements and…
A gel consists of a network of particles or molecules formed for example using the sol-gel process, by which a solution transforms into a porous solid. Particles or molecules in a gel are mainly organized on a scaffold that makes up a…
The vortex-lattice melting transitions in two typical iron-based high-Tc superconductor $Ba(Fe_{1-x}Co_{x})_{2}As_{2}$ (122-type) and$Nd(O_{1-x}F_{x})FeAs$ (1111-type) for magnetic fields both parallel and perpendicular to the anisotropy…
Using a differential magneto-optical technique to visualize flow of transport currents, we reveal a new delocalization line within the reversible vortex liquid region in the presence of a low density of columnar defects. This line separates…
The two-dimensional Hubbard model exhibits superconductivity with d-wave symmetry even at half-filling in the presence of next-nearest neighbor hopping. Using plaquette cluster dynamical mean-field theory with a continuous-time quantum…
We study the stress distribution profiles and the height and thickness fluctuations of lipid membranes in the tilted gel state by Monte Carlo simulations of a generic coarse-grained model for lipid membranes, which reproduces many known…
Superfluid helium is an intimate mixture of a viscous normal fluid, with continuous vorticity, and an inviscid superfluid, where vorticity is constrained to thin, stable topological defects. One mechanism to generate turbulence in this…
We study the phase diagram of flux lines in superconductors with columnar pins. Based on numerical exact diagonalisation simulations on small clusters, we get two phases of vortices: A low temperature pinned glass with diverging tilt…
The range of critical thermal fluctuations in classical bulk superconductors is extremely small and especially in low fields hardly experimentally inaccessible. With a new type of calorimeter we have been able to resolve a small lambda…
The possibility of driving vortex lines with an oscillating magnetic field could be useful in many applications. For example, it can be used for the removal of undesired trapped flux from contactless elements of superconducting devices. We…
It is shown that the transition to the low temperature superconducting state in a 3D metal at high magnetic field is smeared dramatically by thermal fluctuation of the superconducting order parameter. The resulting superconducting-to-normal…
Superfluid condensates are known to occur in contexts ranging from laboratory liquid helium to neutron stars, and are also likely to occur in cosmological phenomena such as axion fields. In the zero temperature limit, such condensates are…
We use a coarse-grained model of superconducting vortices driven through a random pinning potential to study the nonlinear current-voltage (IV) characteristics of flux flow in type II superconductors with pinning. In experiments, the IV…
We numerically investigate the nature of the phase transition of the XY model in the heptagonal lattice with the negative curvature, in comparison to other interaction structures such as a flat two-dimensional (2D) square lattice and a…
Phase fluctuations in finite thickness layered superconducting films are studied theoretically. The model consists of a set of layers, coupled to each other via a gradient-like term in the phase-only action. It is shown that the effective…
Experimental studies of magnetoresistance in thin superconducting strips subject to a perpendicular magnetic field B exhibit a multitude of transitions, from superconductor to insulator and vice versa alternately. Motivated by this…
The thermal fluctations of vortices in a superconductor can be usefully mapped onto the quantum fluctations of a collection of bosons at T=0 moving in 2 dimensions. When the superconductor is a thin platelet with the magnetic field parallel…