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

Abstract

The HfV 2 Ga 4 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. TheMcMillan formula predicts a superconducting critical temperature (T c ) 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, ScV 2 Ga 4 , showing that it has similar electronic properties, but probably with a higher T c than HfV 2 Ga

Elastic anisotropy and thermal properties of extended linear chain compounds MV2Ga4 (M = Sc, Zr, Hf) from ab-initio calculations

“…Thus, we argue that the ZrV 2 Ga 4 compound, once experimentally proved to be a supercondutor, could present a T c compatible with ScV 2 Ga 4 , or even higher, as a consequence of the calculated value of 510.33 K for the Debye temperature and the high elastic wave velocities, which will result in a more effective electron-phonon interaction in the lattice. In the same way, our evaluated sound velocity values reinforce the previous theoretical prediction that ScV 2 Ga 4 presumably consists of an electron-phonon superconductor with a considerable higher T c than HfV 2 Ga 4 [11].…”

“…The directional dependence for ScV 2 Ga 4 and HfV 2 Ga 4 is quite similar in the (001) plane, but the effect of the extended (c) Figure 4: linear chains is felt in the (100) and (110) planes. As observed in a previous work [11], the valence and conduction electronic density along the vanadium chains is larger for ScV 2 Ga 4 than HfV 2 Ga 4 and, therefore, the V-V bonds are stronger in the former compound, explaining its higher Young's modulus along the [001] direction.…”

“…All latice parameters and internal degrees of freedom were relaxed in order to guarantee a ground-state convergence of 10 −5 Ry in total energy and 0.5 mRy/a 0 (a 0 ≈ 0.529 Å) for forces acting on the nuclei. In a previous work [11] we used an all-electron approach, instead of the pseudopotential methodology applied here, in order to obtain the ground-state electronic properties for the HfV 2 Ga 4 and ScV 2 Ga 4 compounds. We found no appreciable differences either in the density of states or in the band structure plots when we compared the two techniques, which we take as an indication of the validity of the present methodology and of the choice of pseudopotentials.…”

“…This compound is interesting and atypical since it exhibits a possible multiband superconducting effect, which fundamentally consists of the opening of two or more superconducting gaps at the Fermi surface below the critical superconducting temperature (T c ) [10]. In fact, HfV 2 Ga 4 is one of the first examples of a non-heavy fermion material with double-jumps in the specific heat, and the two-gap superconductivity is supported by first-principle calculations, that show electrons arising from distinct bands in disconnected sheets of the Fermi surface with very different electronic characters [9,11]. In addition, it was theoretically predicted that the ScV 2 Ga 4 compound is presumably another example of a twoband electron-phonon superconductor with an even higher T c than HfV 2 Ga 4 [11].…”

Squares of gold atoms and linear infinite chains of Cd atoms as building units in the intermetallic phases REAu4Cd2 (RE=La–Nd, Sm) with YbAl4Mo2-type structure

“…Here the Cu atoms occupy the Al sites, while the Mo site is mixed occupied by Cu and Al. The higher congener gallium forms the series REGa 4 Ti 2 [9][10][11][12][13][14] and REGa 4 V 2 [15][16][17][18]. Especially HfGa 4 V 2 and ScGa 4 V 2 of the latter series have intensively been studied with respect to their superconducting properties and elastic anisotropy [17,18].…”