Modulation of ultrafast quasiparticle dynamics in two-dimensional semiconductors

Place: 215 room 'Isabel Rodríguez', second floor, IMDEA Nanociencia.

Abstract: 

In single-layer semiconducting transition metal dichalcogenides (TMDs), strong quantum
confinement and reduced dielectric screening, due to their two-dimensional structure, leads to tightly bound excitons, trions and higher-order bound states. Understanding the temporal
evolution of such complexes after optical excitation and their response to external stimuli is
essential for unlocking their potential in optoelectronic applications.

First, we investigate the influence of electrostatic doping via the field-effect on the ultrafast
dynamics of trions in single-layer TMDs using broadband femtosecond pump-probe microscopy. We study the temporal dynamics of excitons and trions as the primary
hotoexcited species, disentangle the formation of trions from photogenerated vs electrostatically injected charge carriers and discuss the formation of neutral and charged biexcitons.

As a second control parameter, we apply uniaxial strain and observe a modulation of the exciton and charge carrier dynamics via a change in their mobility and interaction with trap sites.