A universal phase diagram for weakly pinned low-T c type-II superconductors is revisited and extended with new proposals. The low-temperature "Bragg glass" phase is argued to transform first into a disordered, glassy phase upon heating. This glassy phase, a continuation of the high-field equilibrium vortex glass phase, then melts at higher temperatures into a liquid. This proposal provides an explanation for the anomalies observed in the peak effect regime of 2H-NbSe 2 and several other low-T c materials which is independent of the * Corresponding Author, Email:menon@imsc.ernet.in † Corresponding Author, Email:shampa@mailhost.tifr.res.in 1 microscopic mechanisms of superconductivity in these systems.

The peak effect ͑PE͒ region in a single crystal of Ca 3 Rh 4 Sn 13 is shown to comprise two discontinuous first-order-like transitions located near its onset and peak positions, in accordance with a stepwise fracturing of the flux-line lattice. Magnetization response to thermal cycling across the onset position produces an open hysteresis loop, consistent with the notion of the fracturing. A thermomagnetic history dependence study shows that the critical current density J c (H,T) is path dependent over a large part of the (H,T) parameter space. This path dependence ceases above the peak position of the peak effect, suggesting a complete amorphization of the flux-line lattice at (T p ,H p ) line. A plausible vortex phase diagram has been constructed for Ca 3 Rh 4 Sn 13 in which phases like an elastic solid, a plastic solid, and pinned and unpinned amorphous states have been identified.

We determine the drag and the momentum diffusion coefficients of heavy fermion in dense plasma. It is seen that in degenerate matter drag coefficient at the leading order mediated by transverse photon is proportional to (E − µ) 2 while for the longitudinal exchange this goes as (E − µ) 3 . We also calculate the longitudinal diffusion coefficient to obtain the Einstein relation in a relativistic degenerate plasma. Finally, finite temperature corrections are included both for the drag and the diffusion coefficients.

The nature of the ferromagnetic, charge, orbital, and antiferromagnetic order in La 0.35 Pr 0.275 Ca 0.375 MnO 3 (LPCMO) on the nano and micro scale was investigated by photoemission electron microscopy (PEEM) and resonant elastic soft x-ray scattering (RSXS). The structure of the ferromagnetic domains around the Curie temperature T C indicates that they nucleate under a high degree of lattice strain, which is brought about by the charge, orbital, and antiferromagnetic order. The combined temperature-dependent PEEM and RSXS measurements suggest that the lattice distortions associated with charge and orbital order are glassy in nature and that phase separation is driven by the interplay between it and the more itinerant charge carriers associated with ferromagnetic metallic order, even well below T C .

The second magnetization peak and the peak effect anomaly coexisting in a given isothermal magnetization hysteresis loop show striking similarities in Ca 3 Rh 4 Sn 13 , a low-T c superconductor and YBa 2 Cu 3 O 7Ϫ␦ , a high-T c superconductor. The observed variation of the hysteresis width with field could imply a modulation in the degree of the plastic deformation of the elastic vortex solid. The characteristics of the high-T c cuprates, such as large Ginzburg number, short coherence length, decoupling of the Josephson coupled pancake vortices, etc., are unlikely to be the cause of the observed behavior.