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Lecture D. van Mechelen

Roster

WhenWhere
19 February 2007 FWN-Building 5118.-152, Nijenborgh 4, 9747 AG, Groningen
Speaker: D. van Mechelen
Affiliation:University of Geneva, Departement de Physique de la Matiere Condensee
Title:Electron-ohonon coupling in Nb doped SrTi1-xO3
Date:Mon Feb 19, 2007
Start:11.00
Location:FWN-Building 5118.-152
Host:B. Noheda
Telephone:+31 50 363 4565

Abstract

One of the major questions in the physics of high temperature superconductors and colossal magnetoresistance materials is to what extent electron-phonon coupling is important for the transport anomalies and for the superconductivity, though a major obstacle in addressing this issue is the complexity of these materials. In order to separate out the electron-phonon coupling we have studied the perovskite SrTi1-xNbxO3 with 0. < x < 0. Here we report a comprehensive study of this system using THz, infrared, and optical spectroscopies, as well as DC and Hall effect measurements. An optical characterization of the electron phonon coupling in SrTiO3 is interesting in its own right, as it may be a model system for polaron formation. The THz and infrared spectra at 7 K reveal a very narrow (less than 2 meV) Drude peak, which spectral weight indicates a mass enhancement for the lowest carrier concentration of about a factor 3 with respect to the unrenormalized band mass mb. We find that upon increasing the charge carrier density the mass-renormalization is suppressed progressively and m*/mb ~ 2 at doping levels of 2%. The ?missing? Drude spectral weight is recovered in a mid-infrared band at around 300 meV. The mass enhancement, the doping dependence thereof, and a mid-infrared Holstein side band, are clear manifestations of electron-phonon coupling.
Last modified:22 October 2012 2.30 p.m.