1202.5219 (Francis B. Wilken et al.)

Impurity-assisted Andreev reflection at a spin-active
half-metal-superconductor interface    [PDF]

Francis B. Wilken, Piet W. Brouwer

The Andreev reflection amplitude at a clean interface between a half-metallic
ferromagnet (H) and a superconductor (S) for which the half metal's
magnetization has a gradient perpendicular to the interface is proportional to
the excitation energy $\varepsilon$ and vanishes at $\varepsilon=0$ [B\'{e}ri
{\em et al.}, Phys.\ Rev.\ B {\bf 79}, 024517 (2009)]. Here we show that the
presence of impurities at or in the immediate vicinity of the HS interface
leads to a finite Andreev reflection amplitude at $\varepsilon=0$. This
impurity-assisted Andreev reflection dominates the low-bias conductance of a HS
junction and the Josephson current of an SHS junction in the long-junction
limit.

View original: http://arxiv.org/abs/1202.5219