1301.1879 (P. Diener et al.)

S-wave superconductivity probed by measuring magnetic penetration depth
and lower critical field of MgCNi$_{3}$ single crystals    [PDF]

P. Diener, Pierre Rodiere, Thierry Klein, Christophe Marcenat, Jozef Kacmarcik, Zuzana Pribulova, D. J. Jang, H. S. Lee, H. G. Lee, S. I. Lee

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.

View original: http://arxiv.org/abs/1301.1879