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arXiv · 1810.09834

Encapsulation Narrows Excitonic Homogeneous Linewidth of Exfoliated MoSe$_2$ Monolayer

Eric W. Martin·Jason Horng·Hanna G. Ruth·Eunice Paik·Michael-Henr Wentzel·Hui Deng·Steven T. Cundiff
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Abstract

The excitonic homogeneous linewidth of an exfoliated monolayer MoSe$_2$ encapsulated in hexagonal boron nitride is directly measured using multidimensional coherent spectroscopy with micron spatial resolution. The linewidth is 0.26 $\pm$ 0.02 meV, corresponding to a dephasing time $T_2 \approx$ 2.5 ps, which is almost half the narrowest reported values for non-encapsulated MoSe$_2$ flakes. We attribute the narrowed linewidth to Coulomb screening by the encapsulated material and suppression of non-radiative processes. Through direct measurements of encapsulated and non-encapsulated monolayers, we confirm that encapsulation reduces the sample inhomogeneity. However, linewidths measured using photoluminescence and linear absorption remain dominated by inhomogeneity, and these linewidths are roughly 5 times larger than the homogeneous linewidth in even the highest-quality encapsulated materials. The homogeneous linewidth of non-encapsulated monolayers is very sensitive to temperature cycling, whereas encapsulated samples are not modified by temperature cycling. The nonlinear signal intensity of non-encapsulated monolayers is degraded by high-power optical excitation, whereas encapsulated samples are very resilient to optical excitation with optical powers up to the point of completely bleaching the exciton.

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Eric W. Martin, Jason Horng, Hanna G. Ruth, Eunice Paik, Michael-Henr Wentzel, Hui Deng, Steven T. Cundiff. 2018-10-23. Encapsulation Narrows Excitonic Homogeneous Linewidth of Exfoliated MoSe$_2$ Monolayer. https://doi.org/10.1103/physrevapplied.14.021002

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