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Session Q10 - HTSC: THEORY OF OBSERVATION OF ORDER PRAMETER SYMETRY
Mixed session, Friday morning, March 24, 8:00
Ballroom A4, San Jose Convention Center
We study the Cooper pair dynamics of the Chakravarty--Anderson model for high T_c oxides based on pair tunneling between layers in a bilayer. We consider both s-wave and d-wave pairing in the individual layers. In both cases, the shape of the gap function around the Fermi surface is very strongly dependent on the strength of the pair tunneling. We find new branches (optical phonon-like modes) involving out-of-phase fluctuations of the phase and amplitude of the order parameters of the two layers. These are in addition to the expected in-phase Anderson--Bogoliubov phase and Littlewood--Varma amplitude modes. The Coulomb interaction does not renormalize the new ``out-of-phase'' phase mode in the q\rightarrow 0 limit. These new modes are the dynamic signature of the Cooper pair tunneling model since their energy and damping depends critically on the relative magnitudes of the Cooper pair tunneling strength ( T_J ) and the layer pairing interaction ( g ), but not significantly on the symmetry of the pairing. The generalization to a trilayer system (which can arise in Bi, Tl, and Hg Cooper oxides) is briefly discussed.
\par \noindent ^* Research supported by NSERC of Canada.