title: Ultrafast hopping dynamics of 5f electrons in the Mott insulator UO₂ studied by femtosecond pump-probe spectroscopy.
abstract: We describe a femtosecond pump-probe study of ultrafast hopping dynamics of 5f electrons in the Mott insulator UO₂ following Mott-gap excitation at temperatures of 5-300 K. Hopping-induced response of the lattice and electrons is probed by transient reflectivity at mid- and above-gap photon energies, respectively. These measurements show an instantaneous hop, subsequent picosecond lattice deformation, followed by acoustic phonon emission and microsecond relaxation. Temperature-dependent studies indicate that the slow relaxation results from Hubbard excitons formed by U³⁺-U⁵⁺ pairs.
authors.affiliation: Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA. yqan@lanl.gov
authors.forename: Yong Q
authors.initials: YQ
authors.lastname: An
authors.forename: Antoinette J
authors.initials: AJ
authors.lastname: Taylor
authors.forename: Steven D
authors.initials: SD
authors.lastname: Conradson
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Trugman
authors.forename: Tomasz
authors.initials: T
authors.lastname: Durakiewicz
authors.forename: George
authors.initials: G
authors.lastname: Rodriguez