ELECTRONIC INSTABILITIES AND LOCALIZATION EFFECTS IN THE QUASI-TWO-DIMENSIONAL MONOPHOSPHATE TUNGSTEN BRONZES (PO2)4(WO3)2m AND KxP4W8O32

摘要

The monophosphate tungsten bronzes (PO2)4(WO3)2m with pentagonal tunnels are quasi-2-D conductors that show charge density wave type electronic instabilities. These series of compounds provide a model system where the low-dimensional character and the average electron concentration are functions of the m parameter. The low m compounds (m=4, 6) show conventional charge density wave instabilities. The m=5 compound exists with two different crystal structures and shows instabilities with slightly different properties. Authors report measurements of transport properties for the compounds m=5, 7, 8, 9. Authors show that, for m>7, these compounds exhibit an upturn of resistivity and field dependence of the magnetoresistance characteristic of quantum interference effects. Authors also report transport properties of the compounds KxP4W8O32 with pseudo-hexagonal tunnels that show electronic instabilities with critical temperatures depending on x. 26 refs.