Title 



Twoband superconductors : extended GinzburgLandau formalism by a systematic expansion in small deviation from the critical temperature
 
Author 



 
Abstract 



We derive the extended GinzburgLandau (GL) formalism for a clean swave twoband superconductor by employing a systematic expansion of the freeenergy functional and the corresponding matrix gap equation in powers of the small deviation from the critical temperature tau = 1  T/Tc. The two lowest orders of this expansion produce the equation for Tc and the standard GL theory. It is shown that in agreement with previous studies, this twoband GL theory maps onto the singleband GL model and thus fails to describe the difference in the spatial profiles of the twoband condensates. We prove that this difference appears already in the leading correction to the standard GL theory, which constitutes the extended GL formalism. We derive linear differential equations that determine the leading corrections to the band order parameters and magnetic field, discuss the validity of these equations, and consider examples of an important interplay between the band condensates. Finally, we present numerical results for the thermodynamic critical magnetic field and temperaturedependent band gaps for recent materials of interest, which are in very good agreement with those obtained from the full BCS approach in a wide temperature range. To this end, we emphasize the advantages of our extended GL theory in comparison with the often used twocomponent GLlike model based on an unreconstructed twoband generalization of the Gor'kov derivation.   
Language 



English
 
Source (journal) 



Physical review : B : condensed matter and materials physics.  Lancaster, Pa, 1998  2015  
Publication 



Lancaster, Pa : 2012
 
ISSN 



10980121 [print]
1550235X [online]
 
Volume/pages 



86:14(2012), 13 p.
 
Article Reference 



144514
 
ISI 



000309776800001
 
Medium 



Eonly publicatie
 
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