title: Witnessing the formation and relaxation of dressed quasi-particles in a strongly correlated electron system.
abstract: The non-equilibrium approach to correlated electron systems is often based on the paradigm that different degrees of freedom interact on different timescales. In this context, photo-excitation is treated as an impulsive injection of electronic energy that is transferred to other degrees of freedom only at later times. Here, by studying the ultrafast dynamics of quasi-particles in an archetypal strongly correlated charge-transfer insulator (La2CuO(4+δ)), we show that the interaction between electrons and bosons manifests itself directly in the photo-excitation processes of a correlated material. With the aid of a general theoretical framework (Hubbard-Holstein Hamiltonian), we reveal that sub-gap excitation pilots the formation of itinerant quasi-particles, which are suddenly dressed by an ultrafast reaction of the bosonic field.
authors.affiliation: 1] Dipartimento di Fisica, Università degli Studi di Trieste, Via Valerio 2, 34127 Trieste, Italy [2] Elettra-Sincrotrone Trieste S.C.p.A., 34149 Basovizza, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Novelli
authors.affiliation: SPIN-CNR and Dipartimento di Fisica, Università di Napoli Federico II, I-80126 Napoli, Italy.
authors.forename: Giulio
authors.initials: G
authors.lastname: De Filippis
authors.affiliation: SPIN-CNR and Dipartimento di Fisica, Università di Napoli Federico II, I-80126 Napoli, Italy.
authors.forename: Vittorio
authors.initials: V
authors.lastname: Cataudella
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Trieste, Via Valerio 2, 34127 Trieste, Italy.
authors.forename: Martina
authors.initials: M
authors.lastname: Esposito
authors.affiliation: II. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Vergara
authors.affiliation: Elettra-Sincrotrone Trieste S.C.p.A., 34149 Basovizza, Italy.
authors.forename: Federico
authors.initials: F
authors.lastname: Cilento
authors.affiliation: Dipartimento di Fisica, Università degli Studi di Trieste, Via Valerio 2, 34127 Trieste, Italy.
authors.forename: Enrico
authors.initials: E
authors.lastname: Sindici
authors.affiliation: CNR-IOM Democritos National Simulation Center and Scuola Internazionale Superiore di Studi Avanzati (SISSA), Via Bonomea 265, 34136 Trieste, Italy.
authors.forename: Adriano
authors.initials: A
authors.lastname: Amaricci
authors.affiliation: 1] I-LAMP (Interdisciplinary Laboratories for Advanced Materials Physics), Università Cattolica del Sacro Cuore, I-25121 Brescia, Italy [2] Department of Physics, Università Cattolica del Sacro Cuore, I-25121 Brescia, Italy.
authors.forename: Claudio
authors.initials: C
authors.lastname: Giannetti
authors.affiliation: Department of Physics, University of Oxford, Oxford OX1 3PU, UK.
authors.forename: Dharmalingam
authors.initials: D
authors.lastname: Prabhakaran
authors.affiliation: ICFO-Institut de Ciencies Fotoniques, Av. Carl Friedrich Gauss, 3, Castelldefels, 08860 Barcelona, Spain.
authors.forename: Simon
authors.initials: S
authors.lastname: Wall
authors.affiliation: 1] Elettra-Sincrotrone Trieste S.C.p.A., 34149 Basovizza, Italy [2] INSTM UdR Trieste-ST, 34149 Basovizza, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Perucchi
authors.affiliation: IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Dal Conte
authors.affiliation: IFN-CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza L. da Vinci 32, 20133 Milano, Italy.
authors.forename: Giulio
authors.initials: G
authors.lastname: Cerullo
authors.affiliation: CNR-IOM Democritos National Simulation Center and Scuola Internazionale Superiore di Studi Avanzati (SISSA), Via Bonomea 265, 34136 Trieste, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Capone
authors.affiliation: 1] RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan [2] RRC 'Kurchatov Institute', 123182 Moscow, Russia.
authors.forename: Andrey
authors.initials: A
authors.lastname: Mishchenko
authors.affiliation: II. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Grüninger
authors.affiliation: 1] RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan [2] Department of Applied Physics, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
authors.forename: Naoto
authors.initials: N
authors.lastname: Nagaosa
authors.affiliation: 1] Dipartimento di Fisica, Università degli Studi di Trieste, Via Valerio 2, 34127 Trieste, Italy [2] Elettra-Sincrotrone Trieste S.C.p.A., 34149 Basovizza, Italy [3] II. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany.
authors.forename: Fulvio
authors.initials: F
authors.lastname: Parmigiani
authors.affiliation: 1] Dipartimento di Fisica, Università degli Studi di Trieste, Via Valerio 2, 34127 Trieste, Italy [2] Elettra-Sincrotrone Trieste S.C.p.A., 34149 Basovizza, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Fausti