Title 



Extended GinzburgLandau formalism : systematic expansion in small deviation from the critical temperature
 
Author 



 
Abstract 



Based on the Gor'kov formalism for a clean swave superconductor, we develop an extended version of the singleband GinzburgLandau (GL) theory by means of a systematic expansion in the deviation from the critical temperature T(c), i.e., tau = 1  T/T(c). We calculate different contributions to the order parameter and the magnetic field: the leading contributions (proportional to tau(1/2) in the order parameter and. t in the magnetic field) are controlled by the standard GL theory, while the nexttoleading terms (proportional to tau(3/2) in the gap and proportional to tau(2) in the magnetic field) constitute the extended GL (EGL) approach. We derive the freeenergy functional for the extended formalism and the corresponding expression for the current density. To illustrate the usefulness of our formalism, we calculate, in a semianalytical form, the temperaturedependent correction to the GL parameter at which the surface energy becomes zero, and analytically, the temperature dependence of the thermodynamic critical field. We demonstrate that the EGL formalism is not just a mathematical extension to the theory: variations of both the gap and the thermodynamic critical field with temperature calculated within the EGL theory are found in very good agreement with the full BCS results down to low temperatures, which dramatically improves the applicability of the formalism compared to its standard predecessor.   
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 



85:1(2012), p. 014502,1014502,17
 
Article Reference 



014502
 
ISI 



000298985100002
 
Medium 



Eonly publicatie
 
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