Transport properties of normal and quasinormal states of poor superconductors

There are some doubts whether materials near the superconductor-insulator transition (SIT), either on the insulating side, or with superconductivity suppressed by the magnetic field, behave like an ordinary metal. Two experiments in which this issue is addressed will be reviewed here, namely, transport measurements in which this issue is addressed will be reviewed here, namely, transport measurements of two different materials: single crystals YBa2Cu3O6+x (x ∼ 0.37)--a representative of the HTS family and amorphous InOx where x is the oxygen content which could be changed through moderate-temperature annealing. The low-temperature normal resistivity ρ(T) of YBaCuO crystals on both sides of SIT behaves as usual bad metal with conductivity below the Mott's minimum value. The amorphous In-O films behave differently. These films with superconductivity do not display any characteristic magnetic field which can be interpreted as Bc2. Instead, they give out an example of a quantum phase transition and follow Fisher's model for the field-tuned SIT in disordered two-dimensional superconductors through they are not precisely two-dimensional and their high-magnetic-field state may not be insulating at all. Apparently, the normal state of InOx films comprises localized Cooper pairs