Insights into the unconventional superconductivity in HfV2Ga4 and ScV2Ga4 from first-principles electronic-structure calculations

The HfV2Ga4 compound was recently reported to exhibit unusual bulk superconducting properties, with the possibility of multiband behavior. To gain insight into its properties, we performed ab initio electronic-structure calculations based on the density functional theory (DFT). Our results show that the density of states at the Fermi energy is mainly composed by V-d states. The McMillan formula predicts a superconducting critical temperature (Tc) of approximately 3.9 K, in excellent agreement with the experimental value at 4.1 K, indicating that superconductivity in this new compound may be explained by the electron-phonon mechanism. Calculated valence charge density maps clearly show directional bonding between Hf and V atoms with 1D highly populated V chains and some ionic character between Hf-Ga and V-Ga bonds. Finally, we have shown that there are electrons occupying two distinct bands at the Fermi level, with different characters, which supports experimental indications of possible multiband superconductivity. Based on the results, we propose the study of a related compound, ScV2Ga4, showing that it has similar electronic properties, but probably with a higher Tc than HfV2Ga4.