Highly Anisotropic in-Plane Excitons in Atomically Thin and Bulklike 1T '-ReSe2

Ashish Arora, Jonathan Noky, Matthias Drueppel, Bhakti Jariwala, Thorsten Deilmann, Robert Schneider, Robert D. Schmidt, Osvaldo Del Pozo-Zamudio, Torsten Stiehm, Arnab Bhattacharya, Peter Krueger, Steffen Michaelis de Vasconcellos, Michael Rohlfing, Rudolf Bratschitsch

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

Atomically thin materials such as graphene or MoS2 are of high in-plane symmetry. Crystals with reduced symmetry hold the promise for novel optoelectronic devices based on their anisotropy in current flow or light polarization. Here, we present polarization-resolved optical transmission and photoluminescence spectroscopy of excitons in 1T '-ReSe2. On reducing the crystal thickness from bulk to a monolayer, we observe a strong blue shift of the optical band gap from 1.37 to 1.50 eV. The excitons are strongly polarized with dipole vectors along different crystal directions, which persist from bulk down to monolayer thickness. The experimental results are well reproduced by ab initio calculations based on the GW-BSE approach within LDA+GdW approximation. The excitons have high binding energies of 860 meV for the monolayer and 120 meV for bulk. They are strongly confined within a single layer even for the bulk crystal. In addition, we find in our calculations a direct band gap in 1T '-ReSe2 regardless of crystal thickness, indicating weak interlayer coupling effects on the band gap characteristics. Our results pave the way for polarization-sensitive applications, such as optical logic circuits operating in the infrared spectral region.
Original languageEnglish
JournalNano letters
Volume17
Issue number5
Pages (from-to)3202-3207
Number of pages6
ISSN1530-6984
DOIs
Publication statusPublished - 2017

Keywords

  • ReSe2
  • Rransition metal dichalcogenides
  • Polarization
  • Excitons
  • Anisotropy
  • GW-BSE

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