urgent seminar

[CM ICTP - Trieste]

CONDENSED MATTER AND STATISTICAL PHYSICS SECTION
	
INFORMAL SEMINAR on   Disorder and strong electron correlations



Thursday, 27 April    -    11:00 a.m.



Room 239,  Main Bldg.- II floor




D. IVANOV   ( Ecole Polytechnique Federale de Lausanne )


"Minigap in superconductor-ferromagnet junctions with inhomogenous 
magnetization"


Abstract


We consider the minigap in a disordered ferromagnet (F) in contact with 
a superconductor (S)  in the situation when the magnetization of the F 
is inhomogeneous in space and noncollinear.  If the magnetization is 
strongly inhomogeneous, it effectively averages out, and the minigap 
survives up to the exchange field $h_c ~ (L/a) E_{Th}$, where $L$ is 
the thickness of the F, $a$ is the scale on which the magnetization 
varies, and $E_{Th}$ is the Thouless energy.  Technically, we use the 
"triplet" version of the Usadel equations including both singlet and 
triplet components of the Green's functions. In many cases, the effect 
of disordered magnetization may be effectively included in the 
conventional Usadel equations as the spin-flip scattering term. In the 
case of low-dimensional magnetic inhomogeneities (we consider spiral 
magnetization as an example),  however, the full set of "triplet" 
equations must be solved.