Europhys. Lett.
Volume 72, Number 3, November 2005
Page(s) 423 - 429
Section Condensed matter: electronic structure, electrical, magnetic, and optical properties
Published online 30 September 2005
Europhys. Lett., 72 (3), pp. 423-429 (2005)
DOI: 10.1209/epl/i2005-10252-6

Unconventional isotope effects as evidence for polaron formation in cuprates

A. 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.).

© EDP Sciences 2005