Heterostructure by Ultrafast Two-dimensional Electronic Spectroscopy

Transition metal dichalcogenide heterostructures (TMD HS) with type II band alignment feature an interlayer exciton formed following interlayer charge transfer (ICT)¹. Interlayer excitons in TMD HS are of great general interest due enticing properties with a variety of device applications, however it is still necessary to carefully characterize the timescales and efficiencies of ICT. To determine the dynamics of ICT with simultaneously high spectral and temporal resolution, we perform two-dimensional electronic spectroscopy (2DES) on a large-area unaligned WS₂/MoS₂ HS at room temperature. Utilizing broadband pulses spanning the main excitonic resonances of the HS with a sub-30 fs instrument response function time, we simultaneously measure the interlayer hole transfer (IHT) and the interlayer electron transfer (IET) processes by resolving the build-up dynamics of interlayer cross peaks in the 2DES maps². We find that both processes are extremely fast and occur on timescale below 100 fs. This work demonstrates the utility of broadband 2DES in studying charge transfer dynamics in TMD HS and serves as a first step in carefully characterizing the dynamics of ICT in TMD HS using 2DES.

1. Rivera, P. et al. Nat. Commun. 6, 6242 (2015); 2. Policht, V. R. et al. manuscript in preparation