Superconductivity in a breathing kagome metals ROs(2) (R = Sc, Y, Lu)

We have successfully synthesized three osmium-based hexagonal Laves compounds ROs(2) (R = Sc, Y, Lu), and discussed their physical properties. LeBail refinement of pXRD data confirms that all compounds crystallize in the hexagonal centrosymmetric MgZn(2)-type structure (P6(3)/mmc, No. 194). The refined lattice parameters are a = b = 5.1791(1) Å and c = 8.4841(2) Å for ScOs(2), a = b = 5.2571(3) Å and c = 8.6613(2) Å for LuOs(2) and a = b = 5.3067(6) Å and c = 8.7904(1) Å for YOs(2). ROs(2) Laves phases can be viewed as a stacking of kagome nets interleaved with triangular layers. Temperature-dependent magnetic susceptibility, resistivity and heat capacity measurements confirm bulk superconductivity at critical temperatures, T(c), of 5.36, 4.55, and 3.47 K for ScOs(2), YOs(2), and LuOs(2), respectively. We have shown that all investigated Laves compounds are weakly-coupled type-II superconductors. DFT calculations revealed that the band structure of ROs(2) is intricate due to multiple interacting d orbitals of Os and R. Nonetheless, the kagome-derived bands maintain their overall shape, and the Fermi level crosses a number of bands that originate from the kagome flat bands, broadened by interlayer interaction. As a result, ROs(2) can be classified as (breathing) kagome metal superconductors.