Condensed Matter Seminar

Tzu-Chieh Wei
University of Illinois, Urbana-Champaign

Thursday, January 11, 2007
1:00 pm in SPL 52

Magnetic-Field Enhancement of Superconductivity

Abstract: Magnetic fields and magnetic impurities are each known to suppress superconductivity. However, as the field quenches (namely, polarizes) the impurities, rich consequences, including field-enhanced superconductivity, can emerge when both effects are present. For the case of superconducting wires and thin films this field-spin interplay is investigated via the Eilenberger-Usadel scheme. Non-monotonic dependence of the critical current on the field (and therefore field-enhanced superconductivity) is found to be possible, even in parameter regimes for which the critical temperature decreases monotonically with increasing field. The developed theory is used to explain the observed enhancement in the critical currents of sub-10-nm wide MoGe and Nb superconducting wires. The results also suggest that magnetic moments are residing on the wire surfaces.