Ultrafast Breathinglike Oscillation in the Exciton Density of ZnSe Quantum Wells

Abstract

The spatial density profile of a low-density exciton ensemble in ZnSe quantum wells shows a breathinglike oscillation on a 30-ps time scale. This breathing results from the emission of the first acoustic phonon at the end of the quasiballistic transport phase of the excitons which reverses their direction of propagation. Since the scattering destroys the phase of the excitonic wave function, one can deduce simultaneously the coherence length and the coherence time of excitonic transport by evaluation of the oscillation measured from a single experiment. The breathing, which can be modeled by Monte Carlo simulations, is quenched for rising lattice temperature, i.e., increasing phonon absorption, and in samples with significant disorder. These results were obtained by time-resolved nanophotoluminescence with 5 ps and 250 nm temporal and spatial resolution, respectively.

Charge carrier dynamics in bulk MoS2 crystal studied by transient absorption microscopy

“…Such a hot carrier diffusion has been observed in other types of semiconductors, such as ZnSe. 29,30 The spatiotemporal resolution of the carrier density also allow us to deduce the carrier lifetime. Figure 4(d) shows the measured carrier density as a function of probe delay with the probe spot overlapped with the pump spot (x = 0).…”

Negative effective excitonic diffusion in monolayer transition metal dichalcogenides

“…(3), negative diffusion. Although also observed in singlespecies studies [38,39], negative diffusions appear usually in multi-component systems (also called uphill diffusion, see e.g. [40][41][42]).…”

Effective Negative Diffusion of Singlet Excitons in Organic Semiconductors

“…Partial negative effective exciton diffusion has been shown in quantum wells 36 and two-dimensional semiconductors (TMDs). 22 However, in these cases the distribution of excited states always remained broader than the laser spot.…”