https://doi.org/10.1140/epjb/e2003-00041-7
Ginzburg-Landau theory and effects of pressure on a two-band superconductor: application to MgB2
Department of Physics, University of Antwerpen (UIA),
Universiteitsplein 1, 2610 Antwerpen, Belgium
Corresponding author: a joseph.betouras@ua.ac.be
Received:
3
September
2002
Revised:
16
December
2002
Published online:
14
February
2003
We present a model of pressure effects
of a two-band superconductor based on a Ginzburg-Landau free energy
with two order parameters.
The parameters of the theory are pressure
as well as temperature dependent. New pressure effects emerge as a result
of the competition between the two bands. The theory then is applied to
MgB2.
We identify two possible scenaria regarding the fate of the two σ
subbands under pressure, depending on whether or not
both subbands are above the Fermi energy at ambient pressure.
The splitting of the two subbands is probably caused by the
distortion. If only one subband is above the Fermi energy
at ambient pressure (scenario I),
application of pressure diminishes the splitting and it is possible
that the lower subband participates in the superconductivity.
The corresponding crossover pressure and
Gr
neisen parameter are estimated. In the second scenario
both bands start above the Fermi energy and they move below it,
either by pressure or via the substitution of Mg by Al. In both scenaria,
the possibility of electronical topological transition is emphasized.
Experimental signatures of
both scenaria are presented and
existing experiments are discussed in the
light of the different physical pictures.
PACS: 74.20.De – Phenomenological theories (two-fluid, Ginzburg-Landau, etc.) / 74.25.Dw – Superconductivity phase diagrams / 74.62.Fj – Pressure effects / 74.70.Ad – Metals; alloys and binary compounds (including A15, MgB2, etc.)
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2003
