title: Enhanced superconductivity by rare-earth metal doping in phenanthrene.
abstract: We successfully synthesized La- and Sm-doped phenanthrene powder samples and observed superconductivity in them at T(c) around 6 K. The T(c)s are 6.1 K for La(1) phenanthrene and 6.0 K for Sm(1) phenanthrene, which are enhanced by about 1 and 0.5 K compared to those in A(3) phenanthrene (A = K and Rb) and in Ae(1.5) phenanthrene (Ae = Sr and Ba) superconductors, respectively. The superconductive shielding fractions for La(1) phenanthrene and Sm(1) phenanthrene are 46.1% and 49.8% at 2 K, respectively. The small effect of doping with the magnetic ion Sm(3+) on T(c) and the positive pressure dependence coefficient of T(c) strongly suggest unconventional superconductivity in the doped phenanthrene superconductors. The charge transfer to organic molecules from dopants of La and Sm induces a redshift of 7 cm(-1) per electron for the mode at 1441 cm(-1) in the Raman spectra, which is almost the same as those observed in A(3) phenanthrene (A = K and Rb) and Ae(1.5) phenanthrene (Ae = Sr and Ba) superconductors.
authors.affiliation: Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China.
authors.forename: X F
authors.initials: XF
authors.lastname: Wang
authors.forename: X G
authors.initials: XG
authors.lastname: Luo
authors.forename: J J
authors.initials: JJ
authors.lastname: Ying
authors.forename: Z J
authors.initials: ZJ
authors.lastname: Xiang
authors.forename: S L
authors.initials: SL
authors.lastname: Zhang
authors.forename: R R
authors.initials: RR
authors.lastname: Zhang
authors.forename: Y H
authors.initials: YH
authors.lastname: Zhang
authors.forename: Y J
authors.initials: YJ
authors.lastname: Yan
authors.forename: A F
authors.initials: AF
authors.lastname: Wang
authors.forename: P
authors.initials: P
authors.lastname: Cheng
authors.forename: G J
authors.initials: GJ
authors.lastname: Ye
authors.forename: X H
authors.initials: XH
authors.lastname: Chen