title: Photo-Induced Bandgap Renormalization Governs the Ultrafast Response of Single-Layer MoS2.
abstract: Transition metal dichalcogenides (TMDs) are emerging as promising two-dimensional (2D) semiconductors for optoelectronic and flexible devices. However, a microscopic explanation of their photophysics, of pivotal importance for the understanding and optimization of device operation, is still lacking. Here, we use femtosecond transient absorption spectroscopy, with pump pulse tunability and broadband probing, to monitor the relaxation dynamics of single-layer MoS2 over the entire visible range, upon photoexcitation of different excitonic transitions. We find that, irrespective of excitation photon energy, the transient absorption spectrum shows the simultaneous bleaching of all excitonic transitions and corresponding red-shifted photoinduced absorption bands. First-principle modeling of the ultrafast optical response reveals that a transient bandgap renormalization, caused by the presence of photoexcited carriers, is primarily responsible for the observed features. Our results demonstrate the strong impact of many-body effects in the transient optical response of TMDs even in the low-excitation-density regime.
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano , Piazza Leonardo da Vinci 32, I-20133 Milano, Italy.
authors.forename: Eva A A
authors.initials: EA
authors.lastname: Pogna
authors.affiliation: Centro S3, Istituto Nanoscienze (NANO), Consiglio Nazionale delle Ricerche (CNR) , via G. Campi 213/a, I-41125 Modena, Italy.
authors.forename: Margherita
authors.initials: M
authors.lastname: Marsili
authors.affiliation: Cambridge Graphene Centre, University of Cambridge , 9 J.J. Thompson Avenue , Cambridge CB3 OFA, United Kingdom.
authors.forename: Domenico
authors.initials: D
authors.lastname: De Fazio
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano , Piazza Leonardo da Vinci 32, I-20133 Milano, Italy.|Istituto di Fotonica e Nanotecnologie (IFN), CNR , Piazza Leonardo da Vinci 32 , I-20133 Milano, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Dal Conte
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano , Piazza Leonardo da Vinci 32, I-20133 Milano, Italy.|Istituto di Fotonica e Nanotecnologie (IFN), CNR , Piazza Leonardo da Vinci 32 , I-20133 Milano, Italy.
authors.forename: Cristian
authors.initials: C
authors.lastname: Manzoni
authors.affiliation: Istituto di Struttura della Materia (ISM), CNR , Via Salaria Km 29.3, I-00016 Monterotondo Stazione, Italy.
authors.forename: Davide
authors.initials: D
authors.lastname: Sangalli
authors.affiliation: Cambridge Graphene Centre, University of Cambridge , 9 J.J. Thompson Avenue , Cambridge CB3 OFA, United Kingdom.
authors.forename: Duhee
authors.initials: D
authors.lastname: Yoon
authors.affiliation: Cambridge Graphene Centre, University of Cambridge , 9 J.J. Thompson Avenue , Cambridge CB3 OFA, United Kingdom.
authors.forename: Antonio
authors.initials: A
authors.lastname: Lombardo
authors.affiliation: Cambridge Graphene Centre, University of Cambridge , 9 J.J. Thompson Avenue , Cambridge CB3 OFA, United Kingdom.
authors.forename: Andrea C
authors.initials: AC
authors.lastname: Ferrari
authors.affiliation: Istituto di Struttura della Materia (ISM), CNR , Via Salaria Km 29.3, I-00016 Monterotondo Stazione, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Marini
authors.affiliation: Dipartimento di Fisica, Politecnico di Milano , Piazza Leonardo da Vinci 32, I-20133 Milano, Italy.|Istituto di Fotonica e Nanotecnologie (IFN), CNR , Piazza Leonardo da Vinci 32 , I-20133 Milano, Italy.
authors.forename: Giulio
authors.initials: G
authors.lastname: Cerullo
authors.affiliation: Centro S3, Istituto Nanoscienze (NANO), Consiglio Nazionale delle Ricerche (CNR) , via G. Campi 213/a, I-41125 Modena, Italy.
authors.forename: Deborah
authors.initials: D
authors.lastname: Prezzi
keywords: many-body perturbation theory; real-time simulations; transient absorption spectroscopy; transition metal dichalcogenides; two-dimensional materials