Influence of thermal fluctuations on the Nernst signal in superconducting (K,Ba)BiO3 single crystals

Thierry Klein (1) , Z. Pribulova (2) , Raoul Piquerel (3) , Hervé Cercellier (1) , Jacques Marcus (4) , C. Marcenat (5)

1 NEEL - MagSup - Magnétisme et Supraconductivité
2 CLTP IEP - Centre of Low Temperature Physics
3 NEEL - QuantECA - Circuits électroniques quantiques Alpes
4 NEEL - AUTOCARAC - Automatisation & caractérisation
5 SPSMS - UMR 9001 - Service de Physique Statistique, Magnétisme et Supraconductivité

We report on the Nernst effect, specific heat and transportmeasurements performed in high quality (K,Ba)BiO3 single crystals close to optimal doping (Tc ∼ 31 K). We show that a nonzero Nernst effect remains visible well above the upper critical field unambiguously deduced from the onset of the specific heat anomaly. This finite Nernst signal is attributed to fluctuations of the amplitude of the order parameter in a region where the free energy is smaller than kBT . Despite the absence of any vortex liquid phase (and hence of any significant phase fluctuations), the field and temperature dependence of the Nernst coefficient is very similar to the one obtained in electron-doped cuprates.

Mots clés: supraconductivité

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

Thierry Klein, Z. Pribulova, Raoul Piquerel, Hervé Cercellier, Jacques Marcus, et al.. Influence of thermal fluctuations on the Nernst signal in superconducting (K,Ba)BiO3 single crystals. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2011, 83, pp.094524. ⟨10.1103/PhysRevB.83.094524⟩. ⟨hal-00957182⟩