|Ultrafast nonlinear phonon response of few-layer hexagonal boron nitride |
Auteur(s): Kang Taehee, Zhang Jia, Kundu Achintya, Reimann Klaus, Woerner Michael, Elsaesser Thomas, Gil B., Cassabois G., Flytzanis Christos, Fugallo Giorgia, Lazzeri Michele, Page Ryan, Jena Debdeep
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Nonequilibrium dynamics of TO phonons and low-frequency interlayer shear modes are mapped in femtosecond mid-infrared pump-probe experiments. Time-resolved changes of TO phonon absorption reveal a TO phonon lifetime of 1.2 ps, while the low-frequency excitations decay with a time constant of approximately 20 ps. The coupling of intralayer TO and interlayer motions manifests in a quasi-instantaneous redshift of the TO phonon resonance by some 10 cm −1. Theoretical calculations account for the coupling scenario and underline the relevance of inter-phonon interactions for the nonlinear phonon response of few-layer materials.