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Volume 214, 2019
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Carrier dynamics and spin–valley–layer effects in bilayer transition metal dichalcogenides

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Abstract

Transition metal dichalcogenides are an interesting class of low dimensional materials in mono- and few-layer form with diverse applications in valleytronic, optoelectronic and quantum devices. Therefore, the general nature of the band-edges and the interplay with valley dynamics is important from a fundamental and technological standpoint. Bilayers introduce interlayer coupling effects which can have a significant impact on the valley polarization. The combined effect of spin–orbit and interlayer coupling can strongly modify the band structure, phonon interactions and overall carrier dynamics in the material. Here we use first-principles calculations of electron–electron and electron–phonon interactions to investigate bilayer MoS2 and WSe2 in both the AA′ and AB stacking configurations. We find that in addition to spin–orbit coupling, interlayer interactions present in the two configurations significantly alter the near-band-edge dynamics. Scattering lifetimes and dynamic behavior are highly material-dependent, despite the similarities and typical trends in TMDCs. Additionally, we capture significant differences in dynamics for the AA′ and AB stacking configurations, with lifetime values differing by up to an order of magnitude between them for MoS2. Further, we evaluate the valley polarization times and find that maximum lifetimes at room temperature are of the scale of 1 picosecond for WSe2 in the AB orientation. These results present a pathway to understanding complex heterostructure configurations and ‘magic angle’ physics in TMDCs.

Graphical abstract: Carrier dynamics and spin–valley–layer effects in bilayer transition metal dichalcogenides

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Article information


Submitted
26 Oct 2018
Accepted
26 Nov 2018
First published
26 Nov 2018

Faraday Discuss., 2019,214, 175-188
Article type
Paper
Author version available

Carrier dynamics and spin–valley–layer effects in bilayer transition metal dichalcogenides

C. J. Ciccarino, C. Chakraborty, D. R. Englund and P. Narang, Faraday Discuss., 2019, 214, 175
DOI: 10.1039/C8FD00159F

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