More than doubled ambient superconducting transition in a heavily compressed aromatic hydrocarbon*

Exploring superconductivity at higher transition temperatures $T_{\mathrm{c}}$s in light elements such as hydrogen and carbon and their organic compounds has long been an attractive issue. Cation-doped aromatic hydrocarbons have been discovered to be superconductive with an increasing $T_{\mathrm{c}}$ by adding more hydrocarbon rings. Here we present a discovery of an enhancement of $T_{\mathrm{c}}$ from the ambient 4.8 K to 12.2 K in compressed Ba$_{\mathrm{1.5}}$Phenanthrene by magnetic susceptibility measurements up to 61 GPa. In contrast to the existence of superconductivity within a very narrow pressure range in fullerides, we find that this organic compound maintains superconductivity at more than doubled ambient $T_{\mathrm{c}}$ even at 61 GPa. A phase transition in the region between 3.0 and 5.4 GPa and an orientational disorder at around 28 GPa are identified using synchrotron X-ray diffraction technique. A nice correction between $T_{\mathrm{c}}$ and the angle between two crystal axes indicates the essential role of electronic correlations.