title: Pressure tuning of an ionic insulator into a heavy electron metal: an infrared study of YbS.
abstract: Optical conductivity [sigma(omega)] of YbS has been measured under pressure up to 20 GPa. Below 8 GPa, sigma(omega) is low since YbS is an insulator with an energy gap between a fully occupied 4f state and an unoccupied conduction (c) band. Above 8 GPa, however, sigma(omega) increases dramatically, developing a Drude component due to heavy carriers and characteristic infrared peaks. It is shown that increasing pressure has caused an energy overlap and hybridization between the c band and 4f state, thus driving the initially ionic and insulating YbS into a correlated metal with heavy carriers.
authors.affiliation: Institute for Solid State Physics, The University of Tokyo, Kashiwa 277-8581, Japan. matunami@spring8.or.jp
authors.forename: M
authors.initials: M
authors.lastname: Matsunami
authors.forename: H
authors.initials: H
authors.lastname: Okamura
authors.forename: A
authors.initials: A
authors.lastname: Ochiai
authors.forename: T
authors.initials: T
authors.lastname: Nanba