Thurs. seminar

[CM ICTP - Trieste]

CONDENSED MATTER SECTION

	
SEMINAR on  Disorder and strong electron correlations



Thursday, 22 March   -    11:00 a.m.



Lecture Room 'C',  Main Bldg.- terrace level



O. DIMITROVA   ( The Abdus Salam I.C.T.P. )

"Theory of 2D superconductor with broken inversion symmetry"

Abstract

	This seminar presents a theory of a phase diagram of a two-dimensional 
spin-orbital superconductor in a parallel magnetic field.  A 
spin-orbital interaction of the Rashba type is known to produce at a 
high magnetic field (and in the absence of impurities) an inhomogeneous 
superconductive phase similar to the Larkin-Ovchinnikov-Fulde-Ferrel 
(LOFF)  state.  We consider the case of a strong Rashba interaction 
with the spin-orbital splitting much larger than the superconductive 
gap, and show that at low temperatures the LOFF-type state is separated 
from the usual homogeneous state by a first-order phase transition 
line.  At higher temperatures another inhomogeneous state, a new 
``helical'' state,  intervenes between the uniform BCS and the 
LOFF-like state.  The superfluid density vanishes in the region around 
the second-order transition line between the BCS and the "helical'' 
state.  Non-magnetic impurities suppress both inhomogeneous states.  
However, once an account is made of the next-order term over the small 
ratio Rashba/Fermi velocity, a relatively long-wave helical modulation 
develops from the BCS state.  This long-wave modulation is stable with 
respect to disorder. In addition, we predict that unusual vortex 
defects with a continuous core exist near the phase boundary between 
the helical and the LOFF-like states.  In particular, in the LOFF-like 
state these defects may carry a half-integer flux.