Superfluid Stiffness of Bogoliubov-de Gennes Disordered Superconductors

by Dr Animesh Panda (University of Regensburg, Germany)

Tuesday 25 Nov 2025, 11:00 → 12:00 Asia/Kolkata

A304 and zoom

In BCS-superconductors, the spectral gap, , the pairing amplitude, , and the mean-field critical temperature, , are essentially identical energy scales. This is no longer the case in the presence of sufficiently strong disorder, where the superconductor-insulator transition (SIT) is approached. To study the effect of disorder, we present numerical results using the microscopic Boguliubov-de Gennes (BdG) Hamiltonian for two-dimensional -wave superconductor in a very broad range of disorder strengths, temperature and particle density. Building upon Ref. [1], we reach system sizes large enough to capture the effect of mesoscopic wavefunction variations on the global response functions. A detailed understanding of the interplay among different energy scales and validity of the dirty BCS limit prediction is discussed.

Recent experiments in strongly disordered ultra-thin NbN films find BCS like behaviour for superfluid stiffness, , before a sharp Berezinski-Kosterlitz-Thouless transition [2]. A comparison of our computational results with the measurements is presented. Eg Δ Tc s DS(T ) References

[1] Matthias Stosiek, Bruno Lang, and Ferdinand Evers.“Self-consistent-field ensembles of disordered Hamiltonians:
Efficient solver and application to superconducting films”. In: Phys. Rev. B 101 (14 Apr. 2020), p. 144503. doi: 10 . 1103 / PhysRevB . 101 . 144503. url: https://link.aps.org/doi/10.1103/PhysRevB.101.144503.

[2] Alexander Weitzel et al. “Sharpness of the Berezinskii-Kosterlitz-Thouless Transition in Disordered NbN Films”. In: 
Phys. Rev. Lett. 131 (18 Nov. 2023), p. 186002. doi: 10.1103/PhysRevLett.131.186002. url: https://link.aps.org/doi/
10.1103/PhysRevLett.131.186002