Details of Grant 

EPSRC Reference:	GR/M98975/01
Title:	BEYOND PERTURBATION THEORY IN DISORDERED SUPERCONDUCTORS
Principal Investigator:	Smith, Dr RA
Other Investigators:
Researcher Co-Investigators:
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Department:	School of Physics and Astronomy
Organisation:	University of Birmingham
Scheme:	Standard Research (Pre-FEC)
Starts:	01 November 1999	Ends:	31 July 2001	Value (£):	51,621
EPSRC Research Topic Classifications:	Materials Characterisation
EPSRC Industrial Sector Classifications:	No relevance to Underpinning Sectors
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Panel History:
Summary on Grant Application Form
Experiments measuring resistance in quasi-1D wires near the superconducting transition have emphasised that we do not properly understand disordered superconductors. A new parquet resummation technique has successfully explained the dependence of transition temperature on wire width, and we intend to straightforwardly extend this method to explain the phase-slip resistance, magnetoresistance and upper critical field in these quasi-1D wires.Although the parquet method allows one to consider non-perturbative effects in disordered superconductors, a full understanding can only result from an effective field theory based on a non-liner sigma model. We propose to continue the development of a new model which is derived directly from the microscopic fermionic action of the system. The first steps here will be to reproduce known results of transition temperature and order parameter suppression by disorder, and to derive a consistent many-body perturbation theory. We will then consider upper critical field behaviour and relate results to those obtained from parquet.The ultimate aim will be to understand the superconductor-insulator transition: scaling behaviour there is understood using 'dirty boson' theories, whilst dependence of properties on disorder requires fermionic models. By developing the correct effective field theory, this proposal should elucidate the relation between the two types of model.
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Organisation Website:	http://www.bham.ac.uk