Electronic Spectrum and Optical Properties of Y-Shaped Kekulé-Patterned Graphene: Band Nesting Resonance as An Optical Signature

Abstract

Employing tight-binding model we investigate the effects of a uniform Y-shaped Kekulé lattice distortion on the electronic spectrum and optical conductivity of graphene. We derive a low-energy effective Hamiltonian which is found to be in excellent agreement with one calculated from a diagonalization of the full tight-binding Hamiltonian. Then using the low-energy Hamiltonian and Kubo formula we obtain an analytical expression for the real part of the optical conductivity used to explore the effects of chemical potential, temperature and on-site and hopping energy deviations in details. In particular we find that Y-shaped Kekué-patterned graphene at finite chemical potential displays a large optical response called band nesting resonance. This effect is shown to be robust against increasing temperature, facilitating its detection as an optical signature for the Y-shaped Kekulé distortion even at room temperature.