Abstract
We calculate the low-frequency optical conductivity of clean metals and superconductors at zero temperature neglecting the effects of impurities and phonons. In general, the frequency and temperature dependences of have very little in common. For small Fermi surfaces in three dimensions (but not in two dimensions) we find, for example, that which corresponds to a scattering rate even in the absence of umklapp scattering when there is no contribution to . In the main part of the paper we discuss in detail the optical conductivity of -wave superconductors in two dimensions where for the smallest frequencies and the umklapp processes typically set in smoothly above a finite threshold smaller than twice the maximal gap . In cases where the nodes are located at , such that direct umklapp scattering among them is possible, one obtains .
- Received 1 April 2005
DOI:https://doi.org/10.1103/PhysRevB.72.104510
©2005 American Physical Society