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TT: Fachverband Tiefe Temperaturen

TT 5: Postersession Superconductivity: Materials - Fabrication and Properties

TT 5.16: Poster

Monday, March 23, 2009, 13:00–16:45, P1A

Electron-Phonon Interaction and Phonon Renormalization in the Lamellar Cobaltate Na_xCoO₂ — •Johannes Knolle¹, Alexander Donkov¹, Ilya Eremin^1,2, and Maxim Korshunov^1,3 — ¹Max-Planck-Institut für Physik komplexer Systeme, 01187 Dresden, Germany — ²Institute für Mathematische und Theoretische Physik, TU Braunschweig, 38106 Braunschweig, Germany — ³Siberian Branch of Russian Academy of Sciences, L.V. Kirensky Institute of Physics, 660036 Krasnoyarsk, Russia

We study theoretically the electron-phonon interaction in Na_xCoO₂. For the A_1g and E_1g phonon modes found in Raman experiments, we calculate the matrix elements of the electron-phonon interaction. Analyzing the feedback effect of the conduction electrons on the phonon frequency ω, we investigate the doping dependence of these two phonon modes. Due to the momentum dependence of the electron-phonon interaction, we find the strongest renormalization of the E_1g mode around the Brillouin zone boundary which should be observed in the neutron scattering. At the same time, the A_1g mode shows the strongest coupling to the conducting electrons around the Γ point and reveals its doping dependence in the Raman experiments. Our results shed light on the possible importance of the electron-phonon interaction in the lamellar sodium cobaltates.