Bandwidth control in a perovskite-type 3d1-correlated metal Ca1-xSrxVO3.: I.: Evolution of the electronic properties and effective mass

Single crystals of the perovskite-type 3d(1) metallic alloy system Ca1-xSrxVO3 were synthesized in order to investigate metallic properties near the Mott transition. The substitution of a Ca2+ ion for a Sr2+ ion reduces the bandwidth W due to a buckling of the V-O-V bond angle from similar to 180 degrees for SrVO3 to similar to 160 degrees for CaVO3. Thus, the value of W can be systematically controlled without changing the number of electrons making Ca1-xSrxVO3: one of the most ideal systems for studying bandwidth effects. The Sommerfeld-Wilson ratio (similar or equal to 2), the Kadowaki-Woods ratio (in the same region as heavy fermion systems), and a large T-2 term in the electric resistivity, even at 300 K, substantiate a large electron correlation in this system, though the effective mass, obtained by thermodynamic and magnetic measurements, shows only a systematic but moderate increase in going from SrVO3 to CaVO3, in contrast to the critical enhancement expected from the Brinkmann-Rice picture. It is proposed that the metallic properties observed in this system near the Mott transition can be explained by considering the effect of a nonlocal electron correlation.