Enhanced Superconductivity by Rare-earth Metal-doping in Phenanthrene
X. F. Wang, X. G. Luo, J. J. Ying, Z. J. Xiang, S. L. Zhang, R. R. Zhang, Y. H. Zhang, Y. J. Yan, A. F. Wang, P. Cheng, G. J. Ye, X. H. Chen
Abstract
We successfully synthesized La- and Sm-doped phenanthrene powder samples and discovered superconductivity at
T
c
around 6 K in them. The
T
c
s are 6.1 K for LaPhenanthrene and 6.0 K for SmPhenanthrene, which are enhanced by about 1 K and 0.5 K compared to those in
A
3
Phenanthrene (
A
=K and Rb) and in
A
e
1.5
Phenanthrene (
Ae
= Sr and Ba) superconductors respectively. The superconductive shielding fractions for LaPhenanthrene and SmPhenanthrene are 46.1%
and49.8
%
at2K,respectively.ThelittleeffectofthedopingofthemagneticionSm
^{3+}
on
T_c
andthepositivepressuredependencecoefficienton
T_{\rm c}
stronglysuggestsunconventionalsuperconductivityinthedopedphenanthrenesuperconductors.ThechargetransfertoorganicmoleculesfromdopantsofLaandSminducesaredshiftof7cm
^{-1}
perelectronforthemodeat1441cm
^{-1}
intheRamanspectra,whichisalmostthesameasthoseobservedin
A_3
Phenanthrene(
A
=KandRb)and
Ae_{1.5}
Phenanthrene(
Ae$ = Sr and Ba) superconductors.