title: Time-resolved HAXPES using a microfocused XFEL beam: From vacuum space-charge effects to intrinsic charge-carrier recombination dynamics.
abstract: Time-resolved hard X-ray photoelectron spectroscopy (trHAXPES) using microfocused X-ray free-electron laser (XFEL, hν = 8 keV) pulses as a probe and infrared laser pulses (hν = 1.55 eV) as a pump is employed to determine intrinsic charge-carrier recombination dynamics in La:SrTiO3. By means of a combination of experiments and numerical N-body simulations, we first develop a simple approach to characterize and decrease XFEL-induced vacuum space-charge effects, which otherwise pose a serious limitation to spectroscopy experiments. We then show that, using an analytical mean-field model, vacuum space-charge effects can be counteracted by pump laser-induced photoholes at high excitation densities. This provides us a method to separate vacuum space-charge effects from the intrinsic charge-carrier recombination dynamics in the time domain. Our trHAXPES results thus open a route to studies of intrinsic charge-carrier dynamics on picosecond time scales with lateral spatial resolution on the micrometer scale.
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany.|RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.
authors.forename: Lars-Philip
authors.initials: LP
authors.lastname: Oloff
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.
authors.forename: Ashish
authors.initials: A
authors.lastname: Chainani
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.|Toyota Technological Institute, Nagoya 468-8511, Japan.
authors.forename: Masaharu
authors.initials: M
authors.lastname: Matsunami
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.|Synchrotron Light Application Center, Saga University, 1 Honjo, Saga 840-8502, Japan.
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Takahashi
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.|JASRI, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Togashi
authors.affiliation: JASRI, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Osawa
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany.
authors.forename: Kerstin
authors.initials: K
authors.lastname: Hanff
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany.
authors.forename: Arndt
authors.initials: A
authors.lastname: Quer
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.|Graduate School of Materials Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan.
authors.forename: Ryuki
authors.initials: R
authors.lastname: Matsushita
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.|Graduate School of Materials Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan.
authors.forename: Ryutaro
authors.initials: R
authors.lastname: Shiraishi
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.|Graduate School of Materials Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan.
authors.forename: Maki
authors.initials: M
authors.lastname: Nagashima
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.|Graduate School of Materials Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan.
authors.forename: Ayato
authors.initials: A
authors.lastname: Kimura
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.|Synchrotron Light Application Center, Saga University, 1 Honjo, Saga 840-8502, Japan.
authors.forename: Kotaro
authors.initials: K
authors.lastname: Matsuishi
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.|JASRI, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198, Japan.
authors.forename: Makina
authors.initials: M
authors.lastname: Yabashi
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.|Graduate School of Materials Science, University of Hyogo, Kamigori-cho, Ako-gun, Hyogo 678-1297, Japan.
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Tanaka
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Milano, Via Celoria 16, 20133 Milano, Italy.
authors.forename: Giorgio
authors.initials: G
authors.lastname: Rossi
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Ishikawa
authors.affiliation: Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, 24098 Kiel, Germany.|RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.
authors.forename: Kai
authors.initials: K
authors.lastname: Rossnagel
authors.affiliation: RIKEN SPring-8 Center, 1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.
authors.forename: Masaki
authors.initials: M
authors.lastname: Oura