fflo
 The program fflo calculates the Fulde-Ferell-Larkin-Ovchinnikov (FFLO) critical field for s- and d-wave superconductors as a function of temperature and film thickness.
Features and DescriptionThe 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.
DownloadThe latest version of fflo is 1.0.
fflo source package: fflo-v1.tar.gz
Installation
Documentation and ResultsA 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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