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Recent photoemission experiments show strong indications of polaron formation in undoped
cuprates. We present a calculation of the electron-phonon coupling in undoped
La2CuO4. Using this coupling we calculate the photoemission spectrum. We show that
this coupling indeed leads to polaron formation and that the width of the phonon sideband
agrees well with experimental data [1]. An important question is how the Coulomb
interaction influences the electron-phonon interaction. Studying the Holstein-Hubbard
model in a DMFT formalism which allows for antiferromagnetism, we find a moderate
suppression of the electron-phonon coupling due to the Coulomb interaction for the
electron Green's function but a strong suppression for the phonon Green's function [2],
consistent with sum rules [3]. Antiferromagnetic correlations are found to be crucial for
these results. As the system is doped, the suppression increases for the electron Green's
function but is reduced for the phonon Green's function [2].
[1] O. Rösch, O. Gunnarsson, X. J. Zhou, T. Yoshida, T. Sasagawa, A. Fujimori, Z. Hussain, Z.-X. Shen and S. Uchida, Phys. Rev. Lett. 95, 227002 (2005). [2] G. Sangiovanni, O. Gunnarsson, E. Koch, C. Castellani, and M. Capone, Phys. Rev. Lett. 97, 04604 (2006). [3] O. Rösch and O. Gunnarsson, Phys. Rev. Lett. 93, 237001 (2004). |
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