For distribution - thanks

[CM ICTP - Trieste]

SEMINAR on   Disorder and strong electron correlations


Thursday, 29 March   -    11:00 a.m.



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



M. SCHIRO'   ( S.I.S.S.A./I.S.A.S. )

"How can superconductivity emerge out of a pseudo-gap metal: A novel 
scenario"

Abstract

	Motivated by the physics of cuprates, many attempts have been recently 
done to understand how high temperature superconductivity may emerge 
out of a pseudo-gap metal.  The puzzle lies in the fact that one should 
naively expect that a pseudo-gap in the normal phase cuts off the 
singularity of the Cooper channel.  Consequently a very strong pairing 
mechanism would be required to turn the pseudo-gap metal into a high 
temperature superconductor.  A similar scenario, although in a 
different context from cuprates, was recently discovered, in the 
framework of the so-called Strongly Correlated Superconductivity (SCS), 
solving by Dynamical Mean Field Theory (DMFT) a two-orbital Hubbard 
model with a Jahn-Teller pairing mechanism.  The DMFT phase diagram has 
revealed a very rich phenomenology where a superconductor with an huge 
gap and a large Drude weight comes out of a pseudo-gapped Non Fermi 
Liquid phase just close to a singlet Mott insulator.  To get a further 
insight into such an appealing scenario, we present in this talk a 
simple analytical ansatz for the low-energy part of the self-energy in 
this model.  Our approach mainly relies on the physical idea that 
symmetry breaking provides the system with a low-energy scale, 
identified with the superconducting gap, that regularizes all 
non-Fermi-liquid singularities of the normal phase, thus restoring 
well-defined quasiparticles within the superconducting phase.  Within 
this scenario, superconductivity seems to be the natural fate of the 
pseudo-gap metal at low temperature, rather then a competitor.  To 
check the ansatz we compare our model self-energy with data coming from 
DMFT as well as from a closely related impurity model.  While the 
former only partially confirm our approach, mainly due to the limited 
energy resolution of DMFT data, the latter strongly support our 
scenario.