Critical Doping for the Onset of a Two-Band Superconducting Ground State in SrTiO 3 − δ

Xiao Lin (1) , German Bridoux (1) , Adrien Gourgout (1) , Gabriel Seyfarth (2) , Steffen Krämer (2) , Marc Nardone (3) , Benoît Fauqué (1, 3) , Kamran Behnia (1)

1 LPEM - Laboratoire de Physique et d'Etude des Matériaux (UMR 8213)
2 LNCMI-G - Laboratoire national des champs magnétiques intenses - Grenoble
3 LNCMI-T - Laboratoire national des champs magnétiques intenses - Toulouse

In doped SrTiO3 superconductivity persists down to an exceptionally low concentration of mobile electrons. This restricts the relevant energy window and possible pairing scenarios. We present a study of quantum oscillations and superconducting transition temperature Tc as the carrier density is tuned from 1017 to 1020  cm−3 and identify two critical doping levels corresponding to the filling thresholds of the upper bands. At the first critical doping, which separates the single-band and the two-band superconducting regimes in oxygen-deficient samples, the steady increase of Tc with carrier concentration suddenly stops. Near this doping level, the energy dispersion in the lowest band displays a downward deviation from parabolic behavior. The results impose new constraints for microscopic pairing scenarios.

Domaines: Supraconductivité [cond-mat.supr-con]

Xiao Lin, German Bridoux, Adrien Gourgout, Gabriel Seyfarth, Steffen Krämer, et al.. Critical Doping for the Onset of a Two-Band Superconducting Ground State in SrTiO 3 − δ. Physical Review Letters, 2014, 112 (20), pp.207002. ⟨10.1103/PhysRevLett.112.207002⟩. ⟨hal-01992211⟩