Weak metal-metal transition in the vanadium oxytelluride Rb1−δV2Te2O

We report the synthesis, crystal structure, physical properties, and first-principles calculations of a vanadium-based oxytelluride ${\mathrm{Rb}}_{1\ensuremath{-}\ensuremath{\delta}}{\mathrm{V}}_{2}{\mathrm{Te}}_{2}\mathrm{O}$ ($\ensuremath{\delta}\ensuremath{\approx}0.2$). The crystal structure bears two-dimensional ${\mathrm{V}}_{2}\mathrm{O}$ square nets sandwiched with tellurium layers, mimicking the structural motifs of cuprate and iron-based superconductors. The material exhibits metallic conductivity with dominant hole-type charge carriers. A weak metal-to-metal transition takes place at $\ensuremath{\sim}100$ K, which is conformably characterized by a slight kink/hump in the electrical resistivity, jumps in the Hall and Seebeck coefficients, a minute drop in the magnetic susceptibility, and a small peak in the heat capacity. Neither Bragg-peak splitting nor superlattice reflections can be detected within the resolution of conventional x-ray diffractions. The band-structure calculations show that $\mathrm{V}\ensuremath{-}3d$ orbitals dominate the electronic states at around Fermi energy where a ${d}_{yz}/{d}_{xz}$ orbital polarization shows up. There are three Fermi-surface sheets that seem unfavorable for nesting. Our results suggest an orbital or spin-density-wave order for the low-temperature state and, upon suppression of the competing order, emergence of superconductivity could be expected.