Dephasing of Cooper pairs and subgap electron transport in   superconducting hybrids
  We argue that electron-electron interactions fundamentally restrict the penetration length of Cooper pairs into a diffusive normal metal (N) from a superconductor (S). At low temperatures this Cooper pair dephasing length $L_\varphi$ remains finite and does not diverge at $T \to 0$. We evaluate the subgap conductance of NS hybrids in the presence of electron-electron interactions and demonstrate that this new length $L_\varphi$ can be directly extracted from conductance measurements in such structures. 
Andrew G. Semenov, Andrei D. Zaikin and Leonid S. Kuzmin
cond-mat.mes-hall cond-mat.supr-con