Transport data on Bi, MoGe and PbBi/Ge homogeneously disordered thin films demonstrate that the critical resistivity Rc at the nominal insulator-superconductor transition is linearly proportional to the normal sheet resistance RN. In addition, the critical magnetic field scales linearly with the superconducting energy gap and is well approximated by Hc2. Because RN is determined at high temperatures and Hc2 is the pair-breaking field, the two immediate consequences are that electron-like quasiparticles populate the insulating side of the transition and that standard phase-only models are incapable of describing the destruction of the superconducting state. As gapless electronic excitations populate the insulating state, the universality class is no longer the three-dimensional XY model, thereby relaxing the constraints that this model imposes on the critical exponents as well as on the critical resistance, namely Rc = RQ = h/4e2. The lack of a unique critical resistance in homogeneously disordered films can be understood in this context. In the light of recent experiments which observe an intervening metallic state separating the insulator from the superconductor in homogeneously disordered MoGe thin films, we argue that the two transitions that accompany the destruction of superconductivity are superconductor to Bose metal in which phase coherence is lost and Bose metal to localized electron insulator via pair breaking.
|Original language||English (US)|
|Number of pages||8|
|Journal||Philosophical Magazine B: Physics of Condensed Matter; Statistical Mechanics, Electronic, Optical and Magnetic Properties|
|State||Published - 2001|
ASJC Scopus subject areas
- Chemical Engineering(all)
- Physics and Astronomy(all)