title: Plasmon dynamics in colloidal Cu₂-xSe nanocrystals.
abstract: The optical response of metallic nanostructures after intense excitation with femtosecond-laser pulses has recently attracted increasing attention: such response is dominated by ultrafast electron-phonon coupling and offers the possibility to achieve optical modulation with unprecedented terahertz bandwidth. In addition to noble metal nanoparticles, efforts have been made in recent years to synthesize heavily doped semiconductor nanocrystals so as to achieve a plasmonic behavior with spectrally tunable features. In this work, we studied the dynamics of the localized plasmon resonance exhibited by colloidal Cu(2-x)Se nanocrystals of 13 nm in diameter and with x around 0.15, upon excitation by ultrafast laser pulses via pump-probe experiments in the near-infrared, with ∼200 fs resolution time. The experimental results were interpreted according to the two-temperature model and revealed the existence of strong nonlinearities in the plasmonic absorption due to the much lower carrier density of Cu(2-x)Se compared to noble metals, which led to ultrafast control of the probe signal with modulation depth exceeding 40% in transmission.
authors.affiliation: Dipartimento di Fisica, Istituto di Fotonica e Nanotecnologie CNR, Politecnico di Milano, Piazza Leonardo da Vinci 32, 20133 Milano, Italy. francesco.scotognella@polimi.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Scotognella
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Della Valle
authors.forename: Ajay Ram
authors.initials: AR
authors.lastname: Srimath Kandada
authors.forename: Dirk
authors.initials: D
authors.lastname: Dorfs
authors.forename: Margherita
authors.initials: M
authors.lastname: Zavelani-Rossi
authors.forename: Matteo
authors.initials: M
authors.lastname: Conforti
authors.forename: Karol
authors.initials: K
authors.lastname: Miszta
authors.forename: Alberto
authors.initials: A
authors.lastname: Comin
authors.forename: Kseniya
authors.initials: K
authors.lastname: Korobchevskaya
authors.forename: Guglielmo
authors.initials: G
authors.lastname: Lanzani
authors.forename: Liberato
authors.initials: L
authors.lastname: Manna
authors.forename: Francesco
authors.initials: F
authors.lastname: Tassone
mesh_terms: D003102:Colloids / Q000737:chemistry*; D003198:Computer Simulation; D003300:Copper / Q000737:chemistry*; D008027:Light; D008422:Materials Testing; D008956:Models, Chemical; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D012542:Scattering, Radiation; D012643:Selenium / Q000737:chemistry*; D020349:Surface Plasmon Resonance / Q000379:methods*
chemical_list: D003102:Colloids; D003300:Copper; D012643:Selenium