Crossover from weakly indirect to direct excitons in atomically thin films of InSe

We perform a \(\mathbf{k \cdot p}\) theory analysis of the spectra of the lowest energy and excited states of the excitons in few-layer atomically thin films of InSe taking into account in-plane electric polarizability of the film and the influence of the encapsulation environment. For the thinner f...

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Bibliographic Details
Published in:arXiv.org 2020-06
Main Authors: Ceferino, Adrián, Kok Wee Song, Magorrian, Samuel J, Zólyomi, Viktor, Fal'ko, Vladimir I
Format: Article
Language:English
Subjects:
Crossovers
Excitons
Momentum
Thin films
Valence band
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Summary:We perform a \(\mathbf{k \cdot p}\) theory analysis of the spectra of the lowest energy and excited states of the excitons in few-layer atomically thin films of InSe taking into account in-plane electric polarizability of the film and the influence of the encapsulation environment. For the thinner films, the lowest-energy state of the exciton is weakly indirect in momentum space, with its dispersion showing minima at a layer-number-dependent wave number, due to an inverted edge of a relatively flat topmost valence band branch of the InSe film spectrum and we compute the activation energy from the momentum dark exciton ground state into the bright state. For the films with more than seven In\(_2\)Se\(_2\) layers, the exciton dispersion minimum shifts to \(\Gamma\)-point.
ISSN:2331-8422
DOI:10.48550/arxiv.2001.04849