Superconductivity in alkali-earth metals doped phenanthrene

TL;DR

This paper reports the discovery of superconductivity in alkali-earth metals doped phenanthrene with critical temperatures around 5.5 K, showing signs of unconventional superconductivity through pressure effects and charge transfer analysis.

Contribution

It is the first demonstration of superconductivity in alkali-earth metals doped phenanthrene, revealing unconventional behavior and specific charge transfer characteristics.

Findings

Superconducting T_c of 5.6 K and 5.4 K for Sr and Ba doped phenanthrene.

Shielding fraction of Ba_1.5 phenanthrene exceeds 65%.

Charge transfer evidenced by Raman spectra shifts.

Abstract

We discover superconductivity in alkali-earth metals doped phenanthrene. The superconducting critical temperatures \emph{T}$_c$ are 5.6 K and 5.4 K for Sr$_{1.5}$phenanthrene and Ba$_{1.5}$phenanthrene, respectively. The shielding fraction of Ba$_{1.5}$phenanthrene exceeds 65%. The Raman spectra show 8 cm$^{-1}$/electron and 7 cm$^{-1}$/electron downshifts for the mode at 1441 cm$^{-1}$ due to the charge transfer to organic molecules from the dopants of Ba and Sr. Similar behavior has been observed in A$_3$phenanthrene and A$_3$C$_{60}$(A = K and Rb). The positive pressure effect in Sr$_{1.5}$phenanthrene and Ba$_{1.5}$phenanthrene together with the lower $T_c$ with larger lattice indicates unconventional superconductivity in this organic system.