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

Abstract 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 (FL) material TiTe 2 , a well-known quasi-1D charge density wave (CDW) material K 0.3 MoO 3 and a quasi-1D non-CDW material Li 0.9 Mo 6 O 17 . With TiTe 2 , 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 K 0.3 MoO 3 and Li 0.9 Mo 6 O 17 show quasi-1D electronic structures with non-FL line shapes. A CDW gap opening is observed for K 0.3 MoO 3 , whereas no gap is observed for Li 0.9 Mo 6 O 17 . We show, however, that the standard CDW theory, even with strong fluctuations, is not sufficient to describe the non-FL line shapes of K 0.3 MoO 3 . 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.