title: Sodium: a charge-transfer insulator at high pressures.
abstract: By first-principles methods we analyze the optical response of transparent dense sodium as a function of applied pressure. We discover an unusual kind of charge-transfer exciton that proceeds from the interstitial distribution of valence electrons. The absorption spectrum is strongly anisotropic, which, just at pressures above the metal-insulator transition, manifests as sodium being optically transparent in one direction but reflective in the other. This result provides key information about the crystal structure of transparent sodium, a new unconventional inorganic electride.
authors.affiliation: Nano-Bio Spectroscopy Group, Departamento Física de Materiales, Universidad del País Vasco, Centro de Física de Materiales CSIC-UPV/EHU-MPC and DIPC, Avenida Tolosa 72, E-20018 San Sebastián, Spain.
authors.forename: Matteo
authors.initials: M
authors.lastname: Gatti
authors.forename: Ilya V
authors.initials: IV
authors.lastname: Tokatly
authors.forename: Angel
authors.initials: A
authors.lastname: Rubio
mesh_terms: D000042:Absorption; D003460:Crystallization; D004579:Electron Transport; D008958:Models, Molecular; D008962:Models, Theoretical; D008968:Molecular Conformation; D055620:Optical Phenomena; D011312:Pressure; D012964:Sodium / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D012964:Sodium