Hirsch-Fye cluster solver

We have developed a DCA computer program based on the Hirsch-Fye QMC cluster solver. The program allows us to calculate the electron and phonon Green's functions as well as the charge and spin susceptibilities and the optical conductivity. The method is being used to study the optical conductivity, resistivity saturation and the phonon spectrum of high T_c superconductors.

The calculation of response functions is of great interest but numerically difficult. This approach is based on solving the Bethe-Salpeter equation, using a cluster approximation for the vertex function. One major complication is that the Hirsch-Fye QMC cluster solver works in the imaginary time domain, while the Bethe-Salpeter equation is solved for imaginary frequencies. This requires a fast and accurate Fourier transform. We have developed an efficient method for performing such transformations (Phys. Rev. B 82, 233104 (2010)).

The method has been used to study the (pseudogap) in high temperature superconductors.

Publications:

O. Gunnarsson, M.W. Haverkort, G. Sangiovanni:
Fourier transformation and response functions,
Phys. Rev. B 82, 233104 (2010).

G. Sangiovanni and O. Gunnarsson:
Isotope effect in the pseudogap state of high-temperature copper-oxide superconductors,
Phys. Rev. B, Rapid Commun. 84, 100505 (2011).

J. Merino and O. Gunnarsson:
Pseudogap in cuprate and organic superconductors,
arXiv:1208.3996.

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For further information contact Olle Gunnarsson (O.Gunnarsson@fkf.mpg.de) or Giorgio Sangiovanni (sangiovanni@ifp.tuwien.ac.at).