Impurity effects on nano-structured dirty superconductors: violation of Anderson’s Theorem

Theory of Dirty Superconductors

A B.C.S. type of theory (see BARDEEX, COOPER and SCHREIFFER, Phys. Rev. 108, 1175 (1957)) is sketched for very dirty superconductors, where elastic scattering from physical and chemical impurities is large compared with the energy gap. This theory is based on pairing each one-electron state with its exact time reverse, a generalization of the k up, -k down pairing of the B.C.S. theory which is ...

Anomalous impurity effects in nonadiabatic superconductors

– We show that, in contrast with the usual electron-phonon Migdal-Eliashberg theory, the critical temperature Tc of an isotropic s-wave nonadiabatic superconductor is strongly reduced by the presence of diluted non-magnetic impurities. Our results suggest that the recently observed Tc-suppression driven by disorder in K3C60 (Phys. Rev. B 55, 3866 (1997)) and in Nd2−xCexCuO4−δ (Phys. Rev. B 58, ...

Impurity Eeects in Superconductors

Pressure effects on Ca60Al40 metallic glass superconductors

Theoretical computation of the pressure dependence superconducting state parameters of binary Ca60Al40 is reported using model potential formalism. Explicit expressions have been derived for the volume dependence of the electron–phonon coupling strength λ and the Coulomb pseudopotential μ* considering the variation of Fermi momentum KF and Debye temperature ӨD with volume. Well known Ashcroft’s...

Quasiparticle localization transition in dirty superconductors

In this paper, a delocalization-localization transition within a superconducting state is explored. The symmetries of the Bogoliubov deGennes Hamiltonian endow the two associated superconducting phases—the thermal metal and the thermal insulator—and the critical point between them, with properties that are in stark contrast with analogous phases in normal systems. Here, for systems preserving s...