In high-Tc cuprate superconductors, the pairing state of electrons is still spin-singlet, as in conventional BCS superconductors. But the orbital part of the wavefunction, order parameter or gap function, has a dx2−y2 symmetry, rather than the isotropic s-wave symmetry. This exotic symmetry has been confirmed by various experiments, especially the phase-sensitive ones. But the underlying mechan...

There are now many nodal superconductors in heavy fermion (HF) systems, charge conjugated organic metals, high Tc cuprates and ruthenates. On the other hand only few of them have well established ∆(k). We present here a study of the angular dependent thermal conductivity in the vortex state of some of the nodal superconductors. We hope it will help to identify the nodal directions in ∆(k) of UP...

The bosonization and duality rules in three-dimensions are applied to analyze some features of superfluids and superconductors. The energy of an ensemble of vortices in a superfluid is recovered by means of a kind of bound which, to some extent, shares similarity with the Bogomol’nyi bound. In the case of superconductors, after recasting the partition function in the form of a pure effective ga...

We establish a condition for the perturbative stability of zero energy nodal points in the quasiparticle spectrum of superconductors in the presence of coexisting commensurate orders. The nodes are found to be stable if the Hamiltonian is invariant under time reversal followed by a lattice translation. The principle is demonstrated with a few examples. Some experimental implications of various ...

New TbFeAs(O,F) and DyFeAs(O,F) superconductors with critical temperatures T(c) = 46 and 45 K and very high critical fields, >or=100 T, have been prepared at 1100-1150 degrees C and 10-12 GPa, demonstrating that high pressure may be used to synthesise late rare earth derivatives of the recently reported RFeAs(O,F) (R = La-Nd, Sm, Gd) high temperature superconductors.

Similar evolutionary variational inequalities appear as convenient formulations for continuous quasistationary models for sandpile growth, formation of a network of lakes and rivers, magnetization of type-II superconductors, and elastoplastic deformations. We outline the main steps of such models derivation and try to clarify the origin of this similarity. New dual variational formulations, ana...

A junction between two topological superconductors containing a pair of Majorana fermions exhibits a "fractional" Josephson effect, 4π periodic in the superconductors' phase difference. An additional fractional Josephson effect, however, arises when the Majorana fermions are spatially separated by a superconducting barrier. This new term gives rise to a set of Shapiro steps which are essentiall...

A number of studies of high-Tc superconductors show that cuprate superconductors have a short coherence length, comparable to the average distance between doped holes. While this observation casts doubt on the applicability of the BCS model, the limit of local pairs is not a good description of the cuprates either, as the existence of a Fermi surface demonstrates. A more appropriate model of a ...

Like the high-Tc copper oxides, organic superconductors are another class of superconductors that cannot be fully explained by the conventional BCS theory, due to the repulsive effective interactions between the charge carriers. Experiments display similarities between these systems and the high-Tc copper oxides in their pairing symmetry and their phase diagram. In this paper, some results from...

Vortex matter in high temperature superconductors has many peculiar properties such as melting of the vortex lattice, creation of new vortex-liquid phases etc. These effects are not seen in conventional superconductors. This is mainly due to the fact that HTc compounds are strongly type two superconductors with Ginzburg-Landau ratio up to ~110 that makes thermal and quantum fluctuations more pr...