Condensed Matter Physics Seminar
Friday, April 9, 1999, 2 p.m.
Plant Sciences Building, Room 1130
Spin polarized tunneling and Andreev reflection in ferromagnet/superconductor
junction
Igor Zutic
(University of Maryland)
Abstract: In recent years it became possible to fabricate
high quality ferromagnet/superconductor (F/S) structures with small interfacial
resistance. Interests in these structures range from examining the basic
properties of spin polarized transport in unconventional superconductors
to the design of novel devices. We study tunneling in F/S junctions
and include the effects of spin polarization, interfacial resistance, and
Fermi wavevector mismatch (FWM) between the F and S regions. Andreev reflection
at the F/S interface, governing tunneling at low bias voltage, is strongly
modified by these parameters. The conductance exhibits a very wide variety
of features as a function of applied voltage. It displays novel behavior,
different from that found in unpolarized tunneling into an unconventional
superconductor or in an F/conventional superconductor junction. We
show that, in the presence of FWM, spin polarization can enhance Andreev
reflection and give rise to a zero bias conductance peak even for an s-wave
superconductor. We discuss possible implications of our results for
interpreting recent experiments [R.J.Soulen et al., Science 282, 84 (1998)]
which measure spin polarization in various materials by examining the behavior
of differential conductance.
Host: Sankar Das Sarma
Back to Condensed Matter Physics Seminar Home
Page