Dirty superconductors and room-temperature superconductivity

It is pointed out that the translation-invariant bipolaron theory of superconductivity can explain the possibility of a metal-superconductor or insulator-superconductor quantum phase transition. The coherence length of a gas of translationally invariant bipolarons is calculated. It is shown that in very dirty superconductors an insulating state characterized by the presence of a coherence peak can be formed. It is concluded that it is impossible for a charge density wave with a non-zero wave vector to propagate in the nodal direction. It is shown that dirty superconductors can be used to create room-temperature superconductivity.