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Unit cell dependence of optical matrix elements in tight-binding theory: The case of zigzag graphene nanoribbons

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Title Unit cell dependence of optical matrix elements in tight-binding theory: The case of zigzag graphene nanoribbons
 
Creator GUNDRA, K
SHUKLA, A
 
Subject GRAPHITE
GAS
Tight-binding theory
Momentum matrix elements
Optical properties
Graphene nanoribbons
 
Description In the tight-binding theory, momentum matrix elements (MMEs) needed to calculate the optical properties are normally computed using a formulation based on the gradient of the Hamiltonian in the k space. We demonstrate the inadequacy of this formulation by considering the case of zigzag graphene nanoribbons. We show that one obtains wrong values of MMEs, in violation of the well-known selection rules, if the unit cell chosen in the calculations does not incorporate the symmetries of the bulk. This is in spite of the fact that the band structure is insensitive to the choice of the unit cell. We substantiate our results based on group-theoretic arguments. Our observations will open an avenue for proper formulation of MMEs. (C) 2011 Elsevier B.V. All rights reserved.
 
Publisher ELSEVIER SCIENCE BV
 
Date 2012-06-26T07:48:11Z
2012-06-26T07:48:11Z
2011
 
Type Article
 
Identifier PHYSICA B-CONDENSED MATTER,406(19)3538-3543
0921-4526
http://dx.doi.org/10.1016/j.physb.2011.06.008
http://dspace.library.iitb.ac.in/jspui/handle/100/14175
 
Language English