High temperature superconductors have in common that they consist of parallel planes of copper oxide separated by layers whose composition can vary. Being ceramics, the cuprate superconductors are poor conductors above the transition temperature, T_c. Below T_c, the parallel Cu-O planes in those materials become superconducting while the layers in between stay poor conductors. Here, we ask to what extent the change in the Casimir energy that arises when the parallel Cu-O layers become superconducting could contribute to the superconducting condensation energy. Our aim here is merely to obtain an order of magnitude estimate. To this end, the material is modelled as consisting below T_c of parallel plasma sheets separated by vacuum and as without a significant Casimir effect above T_c. Due to the close proximity of the Cu-O planes the system is in the regime where the Casimir effect becomes a van der Waals type effect, dominated by contributions from TM surface plasmons propagating along the ab planes. Within this model, the Casimir energy is found to be of the same order of magnitude as the superconducting condensation energy.
Download