Photoemission Spectroscopy of Spinel-Type CuV2S4 Single Crystal

• Published in: Journal of the Physical Society of Japan 2008-11, Vol.77 (11)
• Main Authors: Okada, Hironari, Koyama, Keiichi, Nakatake, Masashi, Shimada, Kenya, Namatame, Hirofumi, Taniguchi, Masaki, Watanabe, Kazuo
• Format: Article
• Language: English
• ISSN: 0031-9015; 1347-4073
• DOI: 10.1143/jpsj.77.114711

We have performed photoemission spectroscopy studies of single-crystalline CuV2S4 using synchrotron radiation, in order to clarify the electronic structure changes across the charge density wave (CDW) transitions in a spinel type compound. Photo-energy-dependent studies show a peak structure just below the Fermi level (EF), which undergoes resonant enhancement at an excitation energy hν=54.5 eV. This energy corresponds to the V 3p-3d threshold energy, thus suggesting that the density of states (DOS) at EF is mainly composed of V 3d states. From temperature-dependent measurements, we observe a reduction in spectral DOS at and near EF, leading to the formation of a pseudogap across CDW transition temperatures. The pseudogap energy scale of ∼0.05 eV, identified at the top of the valence band, is significantly larger than the value expected from a BCS-like transition.