ARPES line shapes in FL and non-FL quasi-low-dimensional inorganic metals

Quasi-low-dimensional (quasi-low-D) inorganic materials are not only ideally suited for angle resolved photoemission spectroscopy (ARPES) but also they offer a rich ground for studying key concepts for the emerging paradigm of non-Fermi liquid (non-FL) physics. In this article, we discuss the ARPES technique applied to three quasi-low-D inorganic metals: a paradigm Fermi liquid (ni) material TiTe2, a well-known quasi-1D charge density wave (CDW) material K0.3MoO3 and a quasi-1D non-CDW material Li0.9Mo6O17. With TiTe2, we establish that a many body theoretical interpretation of the ARPES line shape is possible. We also address the fundamental question of how to accurately determine the k(F) value from ARPES. Both K0.3MoO3 and Li0.9Mo6O17 show quasi-1D electronic structures with non-FL line shapes, A CDW gap opening is observed for K0.3MoO3, whereas no gap is observed for Li0.9Mo6O17. We show, however, that the standard CDW theory, even with strong fluctuations, is not sufficient to describe the non-FL line shapes of K0.3MoO3. We argue that a Luttinger liquid (LL) model is relevant for both bronzes, but also point out difficulties encountered in comparing data with theory. We interpret this situation to mean that a more complete and realistic theory is necessary to understand these data. (C) 2001 Elsevier Science B.V. All rights reserved.