arXiv subjects

A. V. Samoilov

Publications and source records attributed to A. V. Samoilov.

3 recordsLinked to original sources

arXiv2000

Defect-unbinding and the Bose-glass transition in layered superconductors

The low-field Bose-glass transition temperature in heavy-ion irradiated Bi_2Sr_2CaCu_2O_8+d increases progressively with increasing density of irradiation-induced columnar defects, but saturates for densities in excess of 1.5 x10^9 cm^-2. The maximum Bose-glass temperature corresponds to that above which diffusion of two-dimensional pancake vortices between different vortex lines becomes possible, and above which the ``line-like'' character of vortices is lost. We develop a description of the Bose-glass line that is in excellent quantitative agreement with the experimental line obtained for widely different values of track density and material parameters.

cond-mat.supr-con↗

arXiv1999

Phase Diagram of Heavy-Ion Irradiated Bi_2Sr_2CaCu_2O_8

Using dynamic and thermodynamic magnetization measurements, we analyze the phase diagram of Bi_2Sr_2CaCu_2O_8delta single crystals containing amorphous columnar defects created by heavy-ion irradiation. Reversible magnetization experiments yield the respective magnitudes of the pinning energy and entropy contributions to the free energy of the vortex lattice. It appears that the entropy contribution in the London regime is relatively minor in both unirradiated and irradiated crystals, except in the case of high density of columns and inductions B that are smaller than the interaction field H_int ~ B_phi / 6. The dependence of the entropy contribution on vortex- and defect density correlates well with measurements of the irreversibility line H_irr, which shows a sharp increase at H_int.

cond-mat.supr-con↗

arXiv1998

Infrared Studies of a La_{0.67}Ca_{0.33}MnO_3 Single Crystal: Optical Magnetoconductivity in a Half-Metallic Ferromagnet

The infrared reflectivity of a $\rm La_{0.67}Ca_{0.33}MnO_3$ single crystal is studied over a broad range of temperatures (78-340 K), magnetic fields (0-16 T), and wavenumbers (20-9000 cm$^{-1}$). The optical conductivity gradually changes from a Drude-like behavior to a broad peak feature near 5000 cm$^{-1}$ in the ferromagnetic state below the Curie temperature $T_C=307 K$. Various features of the optical conductivity bear striking resemblance to recent theoretical predictions based on the interplay between the double exchange interaction and the Jahn-Teller electron-phonon coupling. A large optical magnetoconductivity is observed near $T_C$.

cond-mat.str-el↗