Unconventional surface impedance of a normal-metal film covering a spin-triplet superconductor due to odd-frequency cooper pairs

Phys Rev Lett. 2011 Aug 19;107(8):087001. doi: 10.1103/PhysRevLett.107.087001. Epub 2011 Aug 16.

Abstract

We discuss the dynamic response of odd-frequency Cooper pairs to an electromagnetic field. By using the quasiclassical Green function method, we calculate the impedance (Z=R-iX) of a normal-metal thin film which covers a superconductor. In contrast with the standard relation (i.e., R≪X), the impedance in spin-triplet proximity structures shows anomalous behavior (i.e., R>X) in the low frequency limit. This unusual relation is a result of the penetration of odd-frequency pairs into the normal metal and reflects the negative Cooper pair density.