Fermi Pressure and Coulomb Repulsion Driven Rapid Hot Plasma Expansion in a van der Waals Heterostructure

• DOI: 10.1021/acs.nanolett.3c00678
• Publication Date: 2023-05-08T12:57:00Z
• Authors: Junho Choi; Jacob Embley; Daria D. Blach; Raül Perea-Causín; Daniel Erkensten; Dong Seob Kim; Long Yuan; Woo Young Yoon; Takashi Taniguchi; Kenji Watanabe; Keiji Ueno; Emanuel Tutuc; Samuel Brem; Ermin Malic; Xiaoqin Li; Libai Huang

Transition metal dichalcogenide heterostructures provide a versatile platform to explore electronic and excitonic phases. As the excitation density exceeds the critical Mott density, interlayer excitons are ionized into an electron-hole plasma phase. The transport of the highly non-equilibrium plasma is relevant for high-power optoelectronic devices but has not been carefully investigated previously. Here, we employ spatially resolved pump-probe microscopy to investigate the spatial-temporal dynamics of interlayer excitons and hot-plasma phase in a MoSe2/WSe2 twisted bilayer. At the excitation density of ∼1014 cm-2, well exceeding the Mott density, we find a surprisingly rapid initial expansion of hot plasma to a few microns away from the excitation source within ∼0.2 ps. Microscopic theory reveals that this rapid expansion is mainly driven by Fermi pressure and Coulomb repulsion, while the hot carrier effect has only a minor effect in the plasma phase.