https://doi.org/10.1140/epjb/e2005-00113-8
Anisotropy of the upper critical field in MgB2: the two-gap Ginzburg-Landau theory
Commissariat à l'Énergie Atomique, DSM/DRFMC/SPSMS,
17 avenue des Martyrs, 38054 Grenoble Cedex 9, France
Corresponding author: a dao@drfmc.ceng.cea.fr
Received:
26
August
2004
Revised:
26
January
2005
Published online:
20
April
2005
The upper critical field in MgB2 is investigated in the framework
of the two-gap Ginzburg-Landau theory. A variational solution of linearized
Ginzburg-Landau equations agrees well with the Landau level expansion
and demonstrates that spatial distributions of the gap functions are different
in the two bands and change with temperature. The temperature variation of the ratio of two gaps
is responsible for the upward temperature dependence of in-plane 
as well as for the deviation of its out-of-plane behavior from the standard angular dependence.
The hexagonal in-plane modulations of can change sign with decreasing temperature.
PACS: 74.70.Ad – Metals; alloys and binary compounds (including A15, MgB2, etc.) / 74.20.De – Phenomenological theories (two-fluid, Ginzburg-Landau etc.) / 74.25.Op – Mixed states, critical fields, and surface sheaths
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2005
