Weak-versus strong-coupling theory for Bi sub 2 Sr sub 2 CaCu sub 2 O sub 8

The latest optical determination of the superconducting-gap function for Bi{sub 2}Si{sub 2}CaCu{sub 2}O{sub 8} is consistent with weak-coupling theory. In contrast, a large discontinuity in heat-capacity data suggests strong-coupling superconductivity, and appears to exceed the theoretical strong-coupling limit. A possible resolution to the apparent incompatibility of the two measurements is presented. The apparent disagreement with the results of strong-coupling theory is also resolved.