Theory for metal hydrides with switchable optical properties

K. K. Ng, F. C. Zhang, V. I. Anisimov, T. M. Rice

Research output: Contribution to journalArticlepeer-review

97 Citations (Scopus)

Abstract

Recently it has been discovered that lanthanum, yttrium, and other metal hydride films show dramatic changes in the optical properties at the metal-insulator transition. Such changes on a high-energy scale suggest the electronic structure is best described by a local model based on negatively charged hydrogen (Formula presented) ions. We develop a many-body theory for the strong correlation in a (Formula presented) ion lattice. The metal hydride is described by a large U limit of an Anderson lattice model. We use lanthanum hydride as a prototype of these compounds, and find that (Formula presented) is an insulator with a substantial gap consistent with experiments. It may be viewed either as a Kondo insulator or a band insulator due to strong electron correlation. A H vacancy state in (Formula presented) is found to be highly localized due to the strong bonding between the electron orbitals of hydrogen and metal atoms. Unlike the impurity states in the usual semiconductors, there is only weak internal optical transitions within the vacancy. The metal-insulator transition takes place in a band of these vacancy states.

Original languageEnglish
Pages (from-to)5398-5413
Number of pages16
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume59
Issue number8
DOIs
Publication statusPublished - 1999
Externally publishedYes

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