Angle Resolved Photoemission and Resonant Photoemission Studies of Quasi Low-Dimensional Oxide Conductors

Abstract

Quasi-low dimensional transition metal oxide conductors have been studied extensively in recent years, but it is only with the advent of high resolution photoemission spectroscopy that the detailed electronic structure of these systems has become accessible [1]. Photoemission spectroscopy provides unique information on these solids, and significant progress has been made recently in understanding electronic states in quasi-low dimensional solids. In this paper we discuss the application of angle resolved photoemission (ARP) to the study of quasi-one dimensional (ID) and quasi-two dimensional (2D) transition metal oxide bronzes, with particular emphasis on their Fermi surfaces and on their defect electronic structure close to the Fermi level (EF). The specific oxides that we have studied are K_0.3MoO₃, Li_0.9Mo₆O₁₇, and Na_0.9Mo₆O₁₇, although many of our conclusions are relevant to all quasi-ID and quasi-2D solids. The physical phenomena characteristic of quasi-1D and quasi-2D solids have been described extensively in this book, as has their modification by defects; consequently they will not be reviewed here. Furthermore, the basic concepts underlying angle integrated photoemission have also been discussed by Malterre in these proceedings. Our focus in this paper will be on the unique information obtained from ARP, namely the k-resolved electronic structure, and from resonant photoemission, namely the orbital character of electronic states.