@article{BimonteHaakhHenkeletal.2010,
  author    = {Bimonte, Giuseppe and Haakh, Harald Richard and Henkel, Carsten and Intravaia, Francesco},
  title     = {Optical BCS conductivity at imaginary frequencies and dispersion energies of superconductors},
  issn      = {1751-8113},
  doi       = {10.1088/1751-8113/43/14/145304},
  year      = {2010},
  abstract  = {We present an efficient expression for the analytic continuation to arbitrary complex frequencies of the complex optical and ac conductivity of a homogeneous superconductor with an arbitrary mean free path. Knowledge of this quantity is fundamental in the calculation of thermodynamic potentials and dispersion energies involving type-I superconducting bodies. When considered for imaginary frequencies, our formula evaluates faster than previous schemes involving Kramers-Kronig transforms. A number of applications illustrate its efficiency: a simplified low-frequency expansion of the conductivity, the electromagnetic bulk self-energy due to longitudinal plasma oscillations, and the Casimir free energy of a superconducting cavity.},
  language  = {en}
}