Disorder-driven superconductor–normal metal phase transition in quasi-one-dimensional organic conductors

Abstract

Effects of nonmagnetic disorder on the critical temperature ${T}_{c}$ and on diamagnetism of quasi-one-dimensional superconductors are reported. The energy of Josephson coupling between wires is considered to be random, which is typical for dirty organic superconductors. We show that this randomness destroys phase coherence between wires and that ${T}_{c}$ vanishes discontinuously at a critical disorder strength. The parallel and transverse components of the penetration depth are evaluated. They diverge at different critical temperatures ${T}_{c}^{(1)}$ and ${T}_{c}$, which correspond to pair breaking and phase-coherence breaking, respectively. The interplay between disorder and quantum phase fluctuations is shown to result in quantum-critical behavior at $T=0$, which manifests itself as a superconducting normal metal phase transition of first order at a critical disorder strength.