Do columnar defects produce bulk pinning?

From magneto-optical imaging performed on heavy-ion-irradiated YBa(2)Cu(3)O(7-delta) single crystals, it is found that at fields and temperatures where strong single vortex pinning by individual irradiation-induced amorphous columnar defects is to be expected, vortex motion is limited by the nucleation of vortex kinks at the specimen surface. In the material bulk, vortex motion occurs through (easy) kink sliding. Depinning in the bulk determines the screening current only at fields comparable to or larger than the matching field, at which the majority of vortices is not trapped by an ion track.     

Resonant scattering and optical properties of intermediate valence Sm1−xYxS

The intermediate-valence state of Sm in Sm_1?xY_xS has been investigated in terms of the d.c. and optical scattering time of the conduction electrons. Strong resonant scattering in the collapsed metallic phase is attributed to the pinning of the Fermi level E_F within a mixed-configuration resonant state. The composition- and temperature dependent electronic phase transition is found to occur when E_F reaches the resonant state.     

New states in SmS ?

Quasihydrostatic pressure resistivity experiments on a single crystal of SmS are reported up to 27.5 kbar. At low temperature, a regime change occurs at P ～ 20 kbar, between a “quasiinsulating” behavior (P < 20 kbar) and a metallic ground state (P 20 kbar). Striking similarities appear with TmSe and TmS cases.     

Intermediate valent metallic SmS and SmSe: A new puzzle

We have discovered that the R-T characteristic of so-called metallic SmS decreases with decreasing T at low temperatures for pressures exceeding?20 kbar. This feature is reminiscent of a metal and in sharp contrast to the previously reported negative temperature coefficient at 10 and 20 kbar. The same fundamental change of the R-T dependence occurs in SmSe at ?100 kbar.