Dark exciton signatures in the infrared transient absorption of MoS2 monolayer
Abstract
Dark excitons play a central role in the nonequilibrium dynamics of two-dimensional semiconductors, but remain difficult to characterize. Transient-absorption experiments, with probes tuned in exciton-exciton transitions energy range (exc-tr-abs), can detect excitations from any populated dark excitons, including symmetry-forbidden, spin-forbidden, and finite-momentum ones. In this work, we develop a GW+BSE scheme for computing exc-tr-abs spectra from arbitrary populated exciton distributions. These dark excitons are included equally by evaluating exciton-exciton dipoles in a locally smooth gauge, including intra- and inter-band contributions. For monolayer MoS2, the exc-tr-abs signal arises from the Γ, K, M, and Q valleys, differing substantially from the Γ-only interpretation. Exciton-exciton dipoles show similar intensities across these valleys, while their weights are dictated by initial excitonic populations. State- and spin-resolved analyses assign the peaks to 1s → 2p and 1s → 3p transitions from both spin-flip and spin-conserving A and B excitons across valleys and momenta.
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BibTeX
@misc{qian2026dark,
title = {{Dark exciton signatures in the infrared transient absorption of MoS$_2$ monolayer}},
author = {Tian-Xiang Qian and Marco d'Alessandro and Claudio Attaccalite and Tian-Yi Cai and Sheng Ju and Davide Sangalli},
howpublished = {HAL},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2608.30504},
eprint = {2608.30504},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05739942v1},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Dark exciton signatures in the infrared transient absorption of MoS_2 monolayer
AU - Tian-Xiang Qian
AU - Marco d'Alessandro
AU - Claudio Attaccalite
AU - Tian-Yi Cai
AU - Sheng Ju
AU - Davide Sangalli
PY - 2026
DA - 2026/09/02
PB - HAL
DO - 10.48550/arxiv.2608.30504
UR - https://hal.science/hal-05739942v1
AB - Dark excitons play a central role in the nonequilibrium dynamics of two-dimensional semiconductors, but remain difficult to characterize. Transient-absorption experiments, with probes tuned in exciton-exciton transitions energy range (exc-tr-abs), can detect excitations from any populated dark excitons, including symmetry-forbidden, spin-forbidden, and finite-momentum ones. In this work, we develop a GW+BSE scheme for computing exc-tr-abs spectra from arbitrary populated exciton distributions. These dark excitons are included equally by evaluating exciton-exciton dipoles in a locally smooth gauge, including intra- and inter-band contributions. For monolayer MoS_2, the exc-tr-abs signal arises from the Γ, K, M, and Q valleys, differing substantially from the Γ-only interpretation. Exciton-exciton dipoles show similar intensities across these valleys, while their weights are dictated by initial excitonic populations. State- and spin-resolved analyses assign the peaks to 1s → 2p and 1s → 3p transitions from both spin-flip and spin-conserving A and B excitons across valleys and momenta.
ER -