Low frequency spectroscopy of the correlated metallic system CaxSr1 -xVO3

Electronic structure of the band-filling-controlled CaVO3 and LaVO3 compounds

We studied the electronic structure of the band-filling CaVO(3) and LaVO(3) compounds. The experimental techniques were photoemission (PES) and x-ray absorption (XAS) spectroscopy. The experimental results were analyzed using an extended cluster model. The ground states of CaVO(3) and LaVO(3) are highly covalent and contain a considerable 3d(n + 1)L contribution. The CaVO(3) compound is in the charge transfer regime (Δ < U), whereas the LaVO(3) material is in the intermediate regime (Δ ∼ U). The spectral weight distributions reveal that CaVO(3) is a coherent metal and that LaVO(3) is a p-d insulator. The photoemission of CaVO(3) shows the coherent peak (3d(1)C) and the incoherent feature (3d(1)L). The spectrum of insulating LaVO(3) presents only the incoherent structure (3d(2)L), whereas the coherent peak is replaced by the Mott-Hubbard screening (3d(2)D). This transfer of spectral weight is responsible for the opening of the experimental bandgap. The incoherent feature contains a considerable O 2p character and cannot be attributed to the lower Hubbard band. Further, the relative V 3d-O 2p cross section helps to explain the photon energy dependence of the PES spectra. The addition spectra of both CaVO(3) and LaVO(3) are dominated by the 3d(n + 1) final state configuration. The distribution of spectral weight is mainly dictated by intra-atomic exchange and crystal field splittings. The coherent contribution is less important than in photoemission, and is greatly diminished in the O 1s x-ray absorption spectra.

Fermi surface of 3d1 perovskite CaVO3 near the Mott transition

We present a detailed de Haas-van Alphen effect study of the perovskite CaVO3, offering an unprecedented test of electronic structure calculations in a 3d transition metal oxide. Our experimental and calculated Fermi surfaces are in good agreement, but only if we ignore large orthorhombic distortions of the cubic perovskite structure. Subtle discrepancies may shed light on an apparent conflict between the low energy properties of CaVO3, which are those of a simple metal, and high energy probes which reveal strong correlations that place CaVO3 on the verge of a metal-insulator transition.