Robust coherent dynamics of homogeneously limited anisotropic excitons in two-dimensional layered ReS2

Rup Kumar Chowdhury; Md Samiul Islam; Marie Barthelemy; Nicolas Beyer; Lorry Engel; Jean-Sebastien Pelle; Mircea Rastei; Alberto Barsella; Francois Fras

arXiv · 2411.13695

Robust coherent dynamics of homogeneously limited anisotropic excitons in two-dimensional layered ReS2

Rup Kumar Chowdhury·Md Samiul Islam·Marie Barthelemy·Nicolas Beyer·Lorry Engel·Jean-Sebastien Pelle·Mircea Rastei·Alberto Barsella·Francois Fras

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Abstract

The discovery of in-plane anisotropic excitons in two-dimensional layered semiconductors enables state-of-the-art nanophotonic applications. A fundamental yet unknown parameter of these quasiparticles is the coherence time (T_2 ), which governs the quantum dephasing timescale, over which the coherent superposition of excitons can be maintained and manipulated. Here, we report the direct measurement of T_2 within the sub-picosecond range, along with multiple population decay timescales (T_1 ) at resonance for anisotropic excitons in pristine layered rhenium disulfide (ReS2). We observe a notable weak dependence on layer thickness for T_2 , and a quasi-independence for T_1 . The excitonic coherence in few-layer ReS2 exhibits exceptional robustness against optical density and temperature compared to other two-dimensional semiconductors, enabling quantum features even at room temperature. No photon echo fingerprints were observed in pristine ReS2, highlighting the homogeneous character of the anisotropic excitonic transitions and a particularly low level of disorder in exfoliated flakes. Lastly, our results for mono- to bulk-like ReS2 support a direct gap band structure regardless their layer thickness, addressing the ongoing discussion about its nature.

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Rup Kumar Chowdhury, Md Samiul Islam, Marie Barthelemy, Nicolas Beyer, Lorry Engel, Jean-Sebastien Pelle, Mircea Rastei, Alberto Barsella, Francois Fras. 2024-11-20. Robust coherent dynamics of homogeneously limited anisotropic excitons in two-dimensional layered ReS2. https://arxiv.org/abs/2411.13695

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