title: Anomalous Metallic State of Cu0.07TiSe2: an optical spectroscopy study.
abstract: We report an optical spectroscopy study on the newly discovered superconductor Cu0.07TiSe2. Consistent with the development from a semimetal or semiconductor with a very small indirect energy gap upon doping TiSe2, it is found that the compound has a low carrier density. Most remarkably, the study reveals a substantial shift of the screened plasma edge in reflectance towards high energy with decreasing temperature. This phenomenon, rarely seen in metals, indicates either a sizable increase of the conducting carrier concentration or/and a decrease of the effective mass of carriers with reducing temperature. We attribute the shift primarily to the latter effect.
authors.affiliation: Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080, People's Republic of China.
authors.forename: G
authors.initials: G
authors.lastname: Li
authors.forename: W Z
authors.initials: WZ
authors.lastname: Hu
authors.forename: J
authors.initials: J
authors.lastname: Dong
authors.forename: D
authors.initials: D
authors.lastname: Qian
authors.forename: D
authors.initials: D
authors.lastname: Hsieh
authors.forename: M Z
authors.initials: MZ
authors.lastname: Hasan
authors.forename: E
authors.initials: E
authors.lastname: Morosan
authors.forename: R J
authors.initials: RJ
authors.lastname: Cava
authors.forename: N L
authors.initials: NL
authors.lastname: Wang