Speaker
Description
We studied the $T$&doping-dependence of the energy-loss function of bilayer and trilayer Bi-cuprate by ellipsometry to obtain information on the energy stored in the Coulomb interaction between the conduction electrons,on the $T$-dependence thereof,and on the change of Coulomb interaction when Cooper-pairs are formed. As $T$ drops through $T_c$,the loss function's integral $\leq2eV$ displays an abrupt change of $T$-dependence as compared to the normal state. This effect at$\simeq T_c$depends on doping,with a sign-change for weak overdoping. Based on our observations we decide whether or not the Superconducting phase transition is driven by the saving of Coulomb energy for small momentum and discus its implications for the mechanism of high$T_c$superconductivity.
