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arXiv · 2205.10303

Highly nonlinear biexcitonic photocurrent from ultrafast inter-layer charge transfer

Sarthak Das·Garima Gupta·Suman Chatterjee·Kenji Watanabe·Takashi Taniguchi·Kausik Majumdar
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Abstract

Strong Coulomb interaction in monolayer semiconductors allows them to host optically active large many-body states, such as the five-particle state, charged biexciton. Strong nonlinear light absorption by the charged biexciton under spectral resonance, coupled with its charged nature, makes it intriguing for nonlinear photodetection - an area that is hitherto unexplored. Using the high built-in vertical electric field in an asymmetrically designed few-layer graphene encapsulated 1L-WS$_2$ heterostructure, here we report a large, highly nonlinear photocurrent arising from the strong absorption by two charged biexciton species under zero external bias (self-powered mode). Time-resolved measurement reveals that the generated charged biexcitons transfer to the few-layer graphene in a timescale of sub-5 ps, indicating an ultrafast intrinsic limit of the photoresponse. By using single- and two-color photoluminescence excitation spectroscopy, we show that the two biexcitonic peaks originate from bright-dark and bright-bright exciton-trion combinations. Such innate nonlinearity in the photocurrent due to its biexcitonic origin, coupled with the ultrafast response due to swift inter-layer charge transfer, exemplifies the promise of manipulating many-body effects in monolayers towards viable optoelectronic applications.

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Sarthak Das, Garima Gupta, Suman Chatterjee, Kenji Watanabe, Takashi Taniguchi, Kausik Majumdar. 2022-05-20. Highly nonlinear biexcitonic photocurrent from ultrafast inter-layer charge transfer. https://arxiv.org/abs/2205.10303

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