Enhanced superconductivity by rare-earth metal doping in phenanthrene

Authors:
  • JYJ J Ying
    J J Ying
  • ZXZ J Xiang
    Z J Xiang
  • SZS L Zhang
    S L Zhang
  • RZR R Zhang
    R R Zhang
  • YZY H Zhang
    Y H Zhang
  • YYY J Yan
    Y J Yan
  • AWA F Wang
    A F Wang
  • PCP Cheng
    P Cheng
  • GYG J Ye
    G J Ye
  • XCX H Chen
    X H Chen
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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.
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