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Title: Communication: Effect of accidental mode degeneracy on Raman intensity in 2D materials: Hybrid functional study of bilayer phosphorene

Abstract

Bulk black phosphorus has two optical phonon modes labeled as A{sub g}{sup 2} and B{sub 2u}, respectively, that are nearly degenerate in frequency. However, density functional theory calculations using local or semi-local functionals cannot reproduce this degeneracy. Here, we propose a hybrid functional approach aided by van der Waals (vdW) force fields, which can accurately describe the lattice dynamic and electronic properties of both bulk and few-layer black phosphorus (phosphorene). Using this approach we show that in bilayer phosphorene, the two Raman modes derived from the B{sub 2u} and A{sub g}{sup 2} modes could exhibit strong resonance as a result of the accidental degeneracy so that both modes could be observed in Raman experiment. Without the mode degeneracy, however, the Raman intensity of the B{sub 2u}-derived mode would be too weak to be observed. We further show that the accidental degeneracy is correlated to the applied strain, which enables Raman spectroscopy to be a powerful tool for characterizing built-in strains in 2D materials, e.g., due to the interaction with substrates, which has emerged as an important issue in vdW epitaxy.

Authors:
;  [1]
  1. Department of Physics, Applied Physics and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)
Publication Date:
OSTI Identifier:
22675960
Resource Type:
Journal Article
Journal Name:
Journal of Chemical Physics
Additional Journal Information:
Journal Volume: 145; Journal Issue: 2; Other Information: (c) 2016 Author(s); Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0021-9606
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; COMPUTER CALCULATIONS; DENSITY FUNCTIONAL METHOD; LAYERS; RAMAN SPECTROSCOPY; TWO-DIMENSIONAL SYSTEMS; VAN DER WAALS FORCES

Citation Formats

Sun, Yi-Yang, and Zhang, Shengbai. Communication: Effect of accidental mode degeneracy on Raman intensity in 2D materials: Hybrid functional study of bilayer phosphorene. United States: N. p., 2016. Web. doi:10.1063/1.4958460.
Sun, Yi-Yang, & Zhang, Shengbai. Communication: Effect of accidental mode degeneracy on Raman intensity in 2D materials: Hybrid functional study of bilayer phosphorene. United States. doi:10.1063/1.4958460.
Sun, Yi-Yang, and Zhang, Shengbai. Thu . "Communication: Effect of accidental mode degeneracy on Raman intensity in 2D materials: Hybrid functional study of bilayer phosphorene". United States. doi:10.1063/1.4958460.
@article{osti_22675960,
title = {Communication: Effect of accidental mode degeneracy on Raman intensity in 2D materials: Hybrid functional study of bilayer phosphorene},
author = {Sun, Yi-Yang and Zhang, Shengbai},
abstractNote = {Bulk black phosphorus has two optical phonon modes labeled as A{sub g}{sup 2} and B{sub 2u}, respectively, that are nearly degenerate in frequency. However, density functional theory calculations using local or semi-local functionals cannot reproduce this degeneracy. Here, we propose a hybrid functional approach aided by van der Waals (vdW) force fields, which can accurately describe the lattice dynamic and electronic properties of both bulk and few-layer black phosphorus (phosphorene). Using this approach we show that in bilayer phosphorene, the two Raman modes derived from the B{sub 2u} and A{sub g}{sup 2} modes could exhibit strong resonance as a result of the accidental degeneracy so that both modes could be observed in Raman experiment. Without the mode degeneracy, however, the Raman intensity of the B{sub 2u}-derived mode would be too weak to be observed. We further show that the accidental degeneracy is correlated to the applied strain, which enables Raman spectroscopy to be a powerful tool for characterizing built-in strains in 2D materials, e.g., due to the interaction with substrates, which has emerged as an important issue in vdW epitaxy.},
doi = {10.1063/1.4958460},
journal = {Journal of Chemical Physics},
issn = {0021-9606},
number = 2,
volume = 145,
place = {United States},
year = {2016},
month = {7}
}