Momentum alignment and the optical valley Hall effect in low-dimensional Dirac materials
Saroka, VA; Hartmann, RR; Portnoi, ME
Date: 9 December 2022
Article
Journal
Journal of Experimental and Theoretical Physics
Publisher
Springer / Pleiades Publishing
Publisher DOI
Abstract
We study the momentum alignment of photoexcited carriers and the optical
control of valley population in gapless and gapped two-dimensional Dirac
materials. The trigonal warping effect leads to the spatial separation of
charge carriers belonging to different valleys upon linearly polarized
high-frequency photoexcitation. Valley ...
We study the momentum alignment of photoexcited carriers and the optical
control of valley population in gapless and gapped two-dimensional Dirac
materials. The trigonal warping effect leads to the spatial separation of
charge carriers belonging to different valleys upon linearly polarized
high-frequency photoexcitation. Valley separation in gapped materials can be
detected by measuring the degree of circular polarization of band-edge
photoluminescence at different sides of the sample or light spot (optical
valley Hall effect). We demonstrate that the celebrated Rashba effect, caused
by substrate-induced system asymmetry, leads to a strong anisotropy in the
low-energy part of the spectrum. This results in optical valley separation by a
linearly polarized excitation at much lower frequencies compared to the
high-energy trigonal warping regime. We also show that the momentum alignment
phenomenon explains the giant enhancement of near-band-edge interband optical
transitions in narrow-gap carbon nanotubes and graphene nanoribbons independent
of the mechanism of the gap formation. These enhanced transitions can be used
in terahertz emitters based on low-dimensional Dirac materials.
Physics and Astronomy
Faculty of Environment, Science and Economy
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