1209.3502 (V. Kozhevnikov et al.)

Size and mass of Cooper pairs determined by low-energy $μ$SR and PNR    [PDF]

V. Kozhevnikov, A. Suter, H. Fritzsche, V. Gladilin, A. Volodin, J. Cuppens, T. Prokscha, E. Morenzoni, M. J. Van Bael, K. Temst, C. Van Haesendonck, J. O. Indekeu

The Pippard coherence length $\xi_0$ (the size of a Cooper pair) in an extreme type-I superconductor was determined directly through high-resolution measurement of the nonlocal electrodynamic effect combining low-energy muon spin rotation spectroscopy and polarized neutron reflectometry. The renormalization factor $Z$=m_cp*/2m (m_cp* and m are the mass of the Cooper pair and the electron, respectively) resulting from the electron-phonon interaction, and the temperature dependent London penetration depth $\lambda_L(T)$ were determined as well. A general expression linking $\xi_0$, $Z$ and $\lambda_L(0)$ is introduced and experimentally verified. This expression allows one to determine experimentally the Pippard coherence length in \textit{any} superconductor, independent of whether the electrodynamics is local or nonlocal, conventional or unconventional.

View original: http://arxiv.org/abs/1209.3502