ESPCI web site
Jeudi 18 Septembre 2014, 14h
Amphi Holweck, Esc C, 1ème etage
Superconductivity and Fermi surface in Tl:PbTe
Lisa Buchauer
LPEM
Lead telluride (PbTe) is a narrow-gap semiconductor which exhibits metallic character and a clear Fermi surface even in the absence of controlled doping. The Fermi surface of p-type PbTe for carrier concentrations below 10^19 holes per cm^3 is known to consist of four ellipsoidal pockets at the L-points of the fcc-Brillouin zone. Furthermore, upon doping with thallium (Tl) PbTe becomes a superconductor above a critical carrier concentration of p=5*10^19 cm^-3, corresponding to a critical doping-level of x(Tl)=0.4%.
In this work, the evolution of the Fermi surface of Tl-doped PbTe for p> 10^19 cm^-3 was explored in order to look for a possible link between emerging superconductivity and a change in Fermi surface topology. Paying particular attention to the critical doping range around x(Tl)=0.4%, a series of seven samples with carrier concentrations between 1.5*10^19 cm^-3 and 9*10^19 cm^-3 was analysed using the Shubnikov-de Haas effect (quantum oscillations in resistivity) as a probe.
Evidence was found that the emergence of a superconducting ground state at a critical carrier concentration is concomitant with the observation of an additional oscillation frequency which we attribute to a new set of twelve ellipsoidal Fermi surface pockets at the Sigma-points of the Brillouin-zone. This has implications for the mechanism of superconductivity in Tl:PbTe.