High-resolution angle-resolved photoemission investigation of potassium and phosphate tungsten bronzes

We have performed high-resolution angle-resolved photoemission spectroscopy (ARPES) and density functional ab initio theoretical calculation to study the electronic structure of potassium (K0.25WO3) and phosphate (P4W12O44) tungsten bronzes. We have experimentally determined the band dispersions and Fermi surface topology of these bronzes and compared with our theoretical calculations and a fair agreement has been seen between them. Our experimental as well as theoretical investigation elucidates the origin of transport anomalies in these bronzes. The Fermi surfaces of these bronzes consist of flat patches, which can be connected with each other by a constant nesting wave vector, q. The scattering wave vectors found from diffraction measurements match with these nesting vectors and the anomalies in the transport properties of these bronzes can be well explained by the evolution of charge-density wave with a partial nesting between the flat segments of the Fermi surfaces.