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hc2
The program hc2 calculates the upper critical field for s- and d-wave
superconductors as a function of temperature and tilt angle of the external field.
The limit of a plane-parallel external field is the FFLO critical field.
Features and Description
The figure shows the comparison of the experimental results on upper critical field
as a function of the tilt angle of the external field of the s-wave superconductor
TaS2 (points, R. C. Morris and R. V. Coleman, Phys.Rev. B7, 991 (1973)) and the
numerical results (lines) of fflo for two temperatures.
The FFLO critical field is the upper critical field (magnetic field causing the
breakdown of superconductivity) of a clean quasi two-dimensional superconductor,
where the external magnetic field lies in the superconducting plane.
The difference between s- and d- wave superconductors lies in the order parameter
(energy gap). The gap of an s-wave superconductor is the same for all wave-vectors
k, while that of a d-wave superconductor has nodes and is thus a function of k.
This results in similar, but different superconducting properties, including a
slightly higher upper critical field for d-wave superconductors.
In a superconductor, two electrons with opposite spin pair up to build a so-called
Cooper-pair. When an external field is switched on, there are two mechanisms that
break up the Cooper-pair: paramagnetic and orbital pair-breaking.
Assuming that the external field lies in the superconducting plane, only
paramagnetic pair-breaking takes effect in a 2d superconductor. Increasing the film
thickness causes an increase in the orbital pair-breaking effect and reduces the
upper critical field, which means that the field, at which superconductivity breaks
down, gets smaller. The same happens when increasing the tilt-angle of the external
field from parallel to perpendicular.
Download
The latest version of hc2 is 1.0
hc2 source package:hc2-v1.tar.gz
Installation
Documentation and Results
A comprehensive documentation on the mathematical and physical background and
results of the programs hc2, hc2d, fflo and free_energy can be read in the
dissertation of Sherryl Manalo
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