Dr. Marie-Aude Méasson Laboratoire Matériaux et Phénomènes Quantiques - CNRS, Université Paris Diderot

Jeudi 3 Juin à 16 h 00 Amphi Holweck, Esc. C, 1er étage

Superconductivity in Non-Centrosymmetric Compounds :
Effect on the upper critical field Hc2 of CeCoGe3

Superconductivity in crystal with non-centrosymmetric structure has recently attracted much
attention notably in heavy fermion compounds, like CePt3Si[1]. The absence of inversion symmetry
along with antisymmetric spin-orbit coupling allows a new kind of superconducting order parameter,
with an admixture of spin-singlet and spin-triplet components [2]. Unconventional properties are
expected, including unusual upper critical field with a helical-vortex state and an anisotropic Pauli
limitation.
I will summarize the theoretical studies on superconductivity in non centrosymmetric
compounds with Rashba type spin-orbit coupling. Then we will focus on experimental results on
CeCoGe3, a non centrosymmetric superconductor. We have studied the upper critical field of
CeCoGe3 and its anisotropy under high pressure. Hc2 is very anisotropic with a huge value for H along
the c axis (dHc2/dT=-45T/K), the highest ever reported if normalized to the superconducting
temperature of 0.65K. A comparison with CePt3Si and other compounds of the same family CeIrSi3
and CeRhSi3 will be done.
[1] E. Bauer et al., Phys. Rev.Lett. 92 (2004) 027003.
[2] Y. Yanase et al., J. Phys. Soc. of Jpn 76 (2007) 124709.
[3] Kimura et al., Phys. Rev. Lett. 98 (2007) 197001.
[4] R. Settai et al., J. Phys. Soc. of Jpn 77 (2008) 073705.

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