Work

Negative diffusivity of excitons in electron–hole plasmas

Year: 2026

Type: article

Abstract: We develop a minimal hydrodynamic framework to describe exciton transport in the presence of an electron-hole plasma in two-dimensional semiconductors. Treating excitons, electrons, and holes as coupled fluids, we show that exciton diffusion is strongly renormalized by momentum exchange with the plasma. In the collisional regime, mutual diffusion leads to a nontrivial redistribution of transport coefficients but preserves the positivity of the exciton diffusivity. In contrast, when plasma inertia and collective charge oscillations are accounted for, the exciton diffusive mode hybridizes with acoustic plasma modes, giving rise to a dynamical instability manifested as an effective negative diffusion coefficient. We demonstrate that this instability originates from the non-equilibrium coupling between slow excitons and fast plasma degrees of freedom, rather than from nonlinear diffusion or thermodynamic effects. Our results provide a unified physical mechanism for negative exciton diffusivity reported in recent experiments and establish collective plasma dynamics as a key control parameter of exciton transport in two-dimensional materials.

Source: Physical Chemistry Chemical Physics

DOI: 10.1039/d6cp02371a

Authors: H. Terças, V. N. Mantsevich

Institutions: University of Lisbon, Universidade Politécnica de Lisboa, Instituto Superior Técnico, Instituto de Plasmas e Fusão Nuclear, Lomonosov Moscow State University

Language: English

Topic: Quantum and electron transport phenomena

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funder: Russian Science Foundation

Award: G6453955964