Phonon contribution on the high Tc Cooper pairing investigated by tunnelling spectroscopy

Nonlocal electron-phonon coupling of ionic charge-fluctuation type and phonon anomalies in high-temperature superconductors

“…Furthermore, as far as the planar oxygen bond-stretching modes are concerned, there is also evidence for the importance of their contribution to Cooper pairing from tunneling spectroscopy on Bi 2 Sr 2 CaCu 2 O 8 . [22][23][24] The physical picture of pairing that arises from the nonlocal EPI effects found to be important for the HTSC by our calculations ͑which neglect spin fluctuations͒ is the following: The first electron of the pair generates an excited system composed of atomic displacements and localized ionic charge fluctuations while the second electron of the pair, retarded in time, is attracted by this formerly excited system consisting of coupled lattice and charge degrees of freedom. Relevant phonon modes for this coupling mechanism are the Cu-in-plane-oxygen bond-stretching modes studied in this paper, which can be treated in adiabatic approximation and, as discussed in Ref.…”

Some Chaotic Points in Cuprate Superconductors

“…According to many researchers, the phenomenon of the critical quantum chaos have been observed in the quasi periodic systems, the systems with two interacting electrons and the fractal matrices (Evangelou & Pichard, 2000;Evangelou, 2001). Furthermore, the superconductors investigated, in which phonon mediated attractive electron-electron interaction leads to form quasi-particles, namely Cooper pairs (Aoki et al, 1996;Egami et al, 2002;Tsudo & Shimada, 2003), constitute a natural laboratory for searching and observing quantum critical chaotic points . In this section, the optimally oxygen doped superconducting samples have been investigated by referring to T c and T PME temperatures extracted from the magnetic susceptibility versus temperature data taken by Quantum Design SQUID susceptometer model MPMS-5S.…”