The anisotropic electron-phonon interaction is used to calculate the transition temperature ${\mathit{T}}_{\mathit{c}}$ of a superconductor. We derive constraints on the maximum value of the anisotropic interaction, and use these extremal values to calculate the maximum increase in ${\mathit{T}}_{\mathit{c}}$ from the anisotropy. Calculations are done for electrons on a two-dimensional square lattice using an Einstein model for phonons.

• Received 22 December 1994

DOI:https://doi.org/10.1103/PhysRevB.51.16452