Unconventional isotope effects as evidence for polaron formation in cupratesA. Bussmann-Holder1, H. Keller2, A. R. Bishop3, A. Simon1, R. Micnas4 and K. A. Müller2
1 Max-Planck-Institute for Solid State Research - Heisenbergstr. 1 D-70569 Stuttgart, Germany
2 Physik-Institut der Universität Zürich - Winterthurerstr. 190 CH-8057 Zürich, Switzerland
3 Los Alamos National Laboratory, Theoretical Division Los Alamos, NM 87545, USA
4 Institute of Physics, A. Mickiewicz University - 85 Umultowska St. 61-614 Poznan, Poland
received 6 June 2005; accepted in final form 9 September 2005
published online 30 September 2005
Unconventional isotope effects (Phys. Rev. Lett., 92 (2004) 057602) as observed in high-temperature superconducting cuprates (HTSC), are explained by polaron formation which leads to a renormalization of the single-particle energies and the formation of density-density interactions. It is shown that the dominant contribution to these effects stems from the coupling to the quadrupolar Q2-type phonon mode.
71.38.-k - Polarons and electron-phonon interactions.
74.20.-z - Theories and models of superconducting state.
74.20.Mn - Nonconventional mechanisms (spin fluctuations, polarons and bipolarons, resonating valence bond model, anyon mechanism, marginal Fermi liquid, Luttinger liquid, etc.).
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