Group theory analysis of phonons in two-dimensional transition metal dichalcogenides

By J. Ribeiro-Soares, R. M. Almeida, E. B. Barros, P. T. Araujo, M. Dresselhaus, L. G. Canccado, A. D. D. F'isica, Universidade Federal de Minas Gerais Department of Electrical Engineering, Computer Science, Massachusetts Institute of Technology Departamento de F'isica and 4 more. 2014

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Transition metal dichalcogenides (TMDCs) have emerged as a new two-dimensional material’s field since the monolayer and few-layer limits show different properties when compared to each other and to their respective bulk materials. For example, in some cases when the bulk material is exfoliated down to a monolayer, an indirect-to-direct band gap in the visible range is observed. The number of layers N (N even or odd) drives changes in space-group symmetry that are reflected in the optical properties. The understanding of the space-group symmetry as a function of the number of layers is therefore important for the correct interpretation of the experimental data. Here we present a thorough group theory study of the symmetry aspects relevant to optical and spectroscopic analysis, for the most common polytypes of TMDCs, i.e., 2 Ha ,2 Hc and 1T ,a s af unction of the number of layers. Real space symmetries, the group of the wave vectors, the relevance of inversion symmetry, irreducible representations of the vibrational modes, optical activity, and Raman tensors are discussed.

Subfields: Inorganic Chemistry, Materials Chemistry

View Paper: https://www.semanticscholar.org/paper/f7234b64b81970201921cf7a928c37c4d07a98c9

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In Inorganic Chemistry

In Materials Chemistry

Citations in the corpus

Production and processing of graphene and related materials (2020, background): “A1` is an out-of-plane vibrational mode and E` is an in-plane one [1322, 1323].”