s-wave superconductivity probed by measuring magnetic penetration depth and lower critical field of MgCNi3 single crystals

Pascale Diener , Pierre Rodiere (1) , Thierry Klein (1) , C. Marcenat (2) , Jozef Kacmarcik (3) , Zuzana Pribulova (3) , D.J. Jang (4) , H.S. Lee (4) , H.G. Lee (5) , S.I. Lee (5)

1 NEEL - MagSup - Magnétisme et Supraconductivité
2 LaTEQS - Laboratoire de Transport Electronique Quantique et Supraconductivité
3 CLTP IEP - Centre of Low Temperature Physics
4 Department of Physics
5 National Creative Research Initiative Center for Superconductivity

The magnetic penetration depth $\lambda$ has been measured in MgCNi$_{3}$ single crystals using both a high precision Tunnel Diode Oscillator technique (TDO) and Hall probe magnetization (HPM). In striking contrast to previous measurements in powders, $\delta\lambda$(T) deduced from TDO measurements increases exponentially at low temperature, clearly showing that the superconducting gap is fully open over the whole Fermi surface. An absolute value at zero temperature $\lambda(0)=$230$\,$nm is found from the lower critical field measured by HPM. We also discuss the observed difference of the superfluid density deduced from both techniques. A possible explanation could be due to a systematic decrease of the critical temperature at the sample surface.

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

Pascale Diener, Pierre Rodiere, Thierry Klein, C. Marcenat, Jozef Kacmarcik, et al.. s-wave superconductivity probed by measuring magnetic penetration depth and lower critical field of MgCNi3 single crystals. Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2009, 79 (22), pp.220508(R). ⟨10.1103/PhysRevB.79.220508⟩. ⟨hal-00771734⟩