Biomedical subjects

R Hlubina

Publications and source records attributed to R Hlubina.

9 recordsLinked to original sources

PubMed2002

First-order transition between a small gap semiconductor and a ferromagnetic metal in the isoelectronic alloy FeSi1-xGex.

The contrasting ground states of isoelectronic, isostructural FeSi and FeGe are explained within an extended local density approximation scheme (LDA+U) by an appropriate choice of the Coulomb repulsion U on the Fe sites. A minimal two-band model with interband interactions leads to a phase diagram for the alloys FeSi1-xGex. A mean field approximation gives a first-order transition between a small gap semiconductor and a ferromagnetic metal as a function of magnetic field, temperature, and concentration x. Unusually the transition from metal to insulator is driven by broadening, not narrowing, the bands and it is the metallic state that shows magnetic order.

Journal Article↗

PubMed2001

Degenerate ground state in a mesoscopic YBa2Cu3O(7-x) grain boundary Josephson junction.

We have measured the current-phase relationship I(varphi) of symmetric 45 degrees YBa2Cu3O7-x grain boundary Josephson junctions. Substantial deviations of the Josephson current from conventional tunnel-junction behavior have been observed: (i) The critical current exhibits, as a function of temperature T, a local minimum at a temperature T*. (ii) At T approximately T*, the first harmonic of I(phi) changes sign. (iii) For T<T*, the second harmonic of I(phi) is comparable to the first harmonic, and (iv) the ground state of the junction becomes degenerate. The results are in good agreement with a microscopic model of Josephson junctions between d-wave superconductors.

Journal Article↗

PubMed1996