Fit file format

A fit file contains a compacted digest of a TCA table, as prescribed by the Odintsov, Semenov and Zorin (OSZ) algorithm. These can be generated with the cf command. Fit files can be used as input to simulators that contain a compatible tunnel junction model (TJM). Presently, WRspice and Synopsys HSPICE can use these files.

An example fit file is shown below.

tcafit  4.2000e+00  1.3696e-03  1.3696e-03 0.008 500  8  0.200 3.9580e-2
-5.55136e+00, 7.35249e-02, 1.28573e+00, 1.08362e+01,-1.58776e-01, 2.87279e+01
-1.24623e-02, 1.00032e+00, 5.84894e-03,-4.50828e-04, 5.81876e-03,-2.11396e-04
-3.83312e-02, 1.00112e+00, 2.10779e-02,-3.09528e-04, 2.13882e-02, 1.13197e-03
-1.18261e-01, 9.98252e-01, 6.29481e-02, 1.95061e-03, 6.04875e-02, 1.68472e-02
-5.41049e-02, 7.52572e-07,-2.72420e-04, 5.67468e+00, 5.43002e-04, 2.37802e+00
-9.94491e-01, 6.50936e-01, 7.80341e-01, 1.14849e-01,-2.36003e-01, 9.49693e-01
-3.42835e-01, 9.60836e-01, 1.75970e-01, 1.81214e-02, 1.47672e-01, 1.40112e-01
-2.80018e-01, 6.49039e-03, 6.26863e-03, 1.81423e-01, 9.20013e-03, 3.23103e-02

The first line is a header, the first word of which is ``tcafit''. The numbers that follow in this line are:

• The temperature in Kelvin (4.2000e+00).
• The left electrode pair-breaking energy in ev (1.3696e-03).
• The right electrode pair-breaking energy in ev (1.3696e-03).
• The smoothing parameter value used to create the TCA table, -s option in the cd command for example (0.008).
• The number of scale points used in the TCA table, -x option in the cd command for example (500).
• The number of terms used in the fit table, -n option in the cf command (8).
• he value of the threshold parameter used when generating the fit parameter table, -h option of the cf command (0.200).
• Normalized quasiparticle current at x=0.8, used to estimate the sub-gap conductance (3.9580e-2).

Following the header line are six columns of real numbers. The number of rows is equal to the ``terms'', which is the -n option to the cf command. The columns are the OSZ parameters P.real, P.imag, A.real, A.imag, B.real, B.imag.