Non-Equilibrium First-Order Exciton Mott Transition at Monolayer Lateral Heterojunctions Visualized by Ultrafast Microscopy

Long Yuan; Biyuan Zheng; Qiuchen Zhao; Roman Kempt; Thomas Brumme; Agnieszka Beata Kuc; Chao Ma; Shibin Deng; Anlian Pan; Libai Huang

arXiv · 2111.07887

Non-Equilibrium First-Order Exciton Mott Transition at Monolayer Lateral Heterojunctions Visualized by Ultrafast Microscopy

Long Yuan·Biyuan Zheng·Qiuchen Zhao·Roman Kempt·Thomas Brumme·Agnieszka Beata Kuc·Chao Ma·Shibin Deng·Anlian Pan·Libai Huang

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Abstract

Atomically precise lateral heterojunctions based on transition metal dichalcogenides provide a new platform for exploring exciton Mott transition in one-dimension. To investigate the intrinsically non-equilibrium Mott transition, we employed ultrafast microscopy with ~ 200 fs temporal resolution to image the transport of different exciton phases in a type II WSe2-WS1.16Se0.84 lateral heterostructure. These measurements visualized the extremely rapid expansion of a highly non-equilibrium electron-hole (e-h) plasma phase with a Fermi velocity up to 3.2*10^6 cm*s-1. An abrupt first-order exciton Mott transition at a density of ~ 5*10^12 cm-2 at room temperature was revealed by ultrafast microscopy, which could be disguised as a continuous transition in conventional steady-state measurements. These results point to exciting new opportunities for designing atomically thin lateral heterojunctions as novel highways of excitons and collective e-h plasma for high-speed electronic applications.

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Long Yuan, Biyuan Zheng, Qiuchen Zhao, Roman Kempt, Thomas Brumme, Agnieszka Beata Kuc, Chao Ma, Shibin Deng, Anlian Pan, Libai Huang. 2021-11-15. Non-Equilibrium First-Order Exciton Mott Transition at Monolayer Lateral Heterojunctions Visualized by Ultrafast Microscopy. https://arxiv.org/abs/2111.07887

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