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Tunable surface plasmons in Weyl semimetals TaAs and NbAs

TitleTunable surface plasmons in Weyl semimetals TaAs and NbAs
Publication TypeJournal Article
Year of Publication2019
AuthorsG. Chiarello, J. Hofmann, Z. Li, V. Fabio, L. Guo, X. Chen, S. Das Sarma, and A. Politano
JournalPhys. Rev. B
Volume99
Pagination121401
Date PublishedMAR 4
Type of ArticleArticle
ISSN2469-9950
Abstract

By means of high-resolution electron energy loss spectroscopy, we investigate the low-energy excitation spectrum of transition-metal monopnictides hosting Weyl fermions. We observe gapped plasmonic modes in (001)-oriented surfaces of single crystals of NbAs and TaAs at 66 and 68 meV, respectively. Our findings are consistent with theory and we estimate an effective Coulomb interaction strength alpha(eff) approximate to 0.41 for both samples. We also demonstrate that the modification of the surface of transition-metal monopnictides by the adsorption of chemical species (in our case, oxygen and hydrocarbon fragments) changes the frequency of the plasmonic excitations, with a subsequent modification of the effective interaction strength in the 0.30-0.48 range. The remarkable dependence of plasmonic features on the presence of adsorbates paves the way for plasmonic sensors based on Weyl semimetals operating in the mid-infrared.

DOI10.1103/PhysRevB.99.121401