Anisotropy of the Sommerfeld Coefficient in Magnesium Diboride Single Crystals

Z. Pribulova , Thierry Klein (1) , Jacques Marcus (2) , C. Marcenat (3) , F. Levy-Bertrand (3) , M. S. Park (4) , H. G. Lee (4) , B.W. Kang (4) , S. I. Lee (4) , S. Tajima (5) , S. Lee (6)

1 NEEL - MagSup - Magnétisme et Supraconductivité
2 NEEL - AUTOCARAC - Automatisation & caractérisation
3 SPSMS - UMR 9001 - Service de Physique Statistique, Magnétisme et Supraconductivité
4 NVCRICS
5 Department of Physics
6 SRL - Superconductivity Research Laboratory

The anisotropic field dependence of the Sommerfeld coefficient has been measured down to B ! 0 by combining specific heat and Hall probe magnetization measurements in MgB2 single crystals. We find that B; is the sum of two contributions arising from the and band, respectively. We show that B; B=Bc2 where Bc2 Bab c2= si n 2 2cos2 p with 5:4 ( being the angle between the applied field and the c axis) and B; B B=B B . The ''critical field'' of the band B is fully isotropic but field dependent increasing from 0:25 T for B 0:1 T up to 3 T Bcc 2 for B ! 3 T. Because of the coupling of the two bands, superconductivity survives in the band up to 3 T but is totally destroyed above for any orientation of the field.

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

Z. Pribulova, Thierry Klein, Jacques Marcus, C. Marcenat, F. Levy-Bertrand, et al.. Anisotropy of the Sommerfeld Coefficient in Magnesium Diboride Single Crystals. Physical Review Letters, 2007, 98 (13), pp.137001. ⟨10.1103/PhysRevLett.98.137001⟩. ⟨hal-00957175⟩