Trion Photoluminescence and Trion Stability in Atomically Thin Semiconductors

• DOI: 10.1103/physrevlett.132.036903
• Publication Date: 2024-01-17T18:06:54Z
• Authors: Raul Perea-Causin; Samuel Brem; Ole Schmidt; Ermin Malic
• Keywords: Condensed Matter - Mesoscale and Nanoscale Physics; Atom and Molecular Physics and Optics; Mesoscale and Nanoscale Physics (cond-mat.mes-hall); FOS: Physical sciences; Condensed Matter Physics; 01 natural sciences; 0104 chemical sciences

The optical response of doped monolayer semiconductors is governed by trions, i.e. photoexcited electron-hole pairs bound to doping charges. While their photoluminescence (PL) signatures have been identified in experiments, a microscopic model consistently capturing bright and dark trion peaks is still lacking. In this work, we derive a generalized trion PL formula on a quantum-mechanical footing, considering direct and phonon-assisted recombination mechanisms. We show the trion energy landscape in WSe2 by solving the trion Schrödinger equation. We reveal that the mass imbalance between equal charges results in less stable trions exhibiting a small binding energy and, interestingly, a large energetic offset from exciton peaks in PL spectra. Furthermore, we compute the temperature-dependent PL spectra for n- and p-doped monolayers and predict yet unobserved signatures originating from trions with an electron at the Λ point. Our work presents an important step toward a microscopic understanding of the internal structure of trions determining their stability and optical fingerprint.

Published by the American Physical Society 2024