Inelastic tunneling of Cooper pairs in c-direction in BSCCO single Josephson junctions and stacks

A reproducible fine structure at subgap voltages in, the I(U) -characterist ics of BSCCO single Josephson junctions and stacks has been observed and in vestigated. The structure is detectable only in the presence of an AC Josep hson current. The overall form of the fine structure is in good agreement w ith the Raman scattering spectra of the optical phonon modes in. this mater ial. We attribute this structure to an inelastic (phonon assisted) tunnelin g of Cooper pairs, which is accompanied by the emission of coherent Raman-a ctive optical phonons at resonance voltages U-res = (h) over bar omega(phon )/2e. The observed structure can. be explained in terms of a theoretical mo del developed by Maksimov, Arseyev and Maslova.