Unconventional gapless semiconductor in an extended martini lattice in covalent honeycomb materials

TL;DR

This paper explores an extended martini lattice model in covalent honeycomb materials, revealing a tunable gapless semiconductor with a flat band at the Fermi level, through theoretical and computational methods.

Contribution

It introduces a new electronic structure in extended martini lattices and demonstrates its realization in graphene and silicene via chemisorption, expanding possibilities for exotic electronic functionalities.

Findings

Identification of a flat band at the Fermi level in the gapless semiconductor

Electronic structures tunable by hopping parameters and atomic species

Potential realization in chemisorbed graphene and silicene

Abstract

We study characteristic electronic structures in an extended martini lattice model and propose its materialization in $\pi$-electron networks constructed by designated chemisorption on graphene and silicene. By investigating the minimal tight-binding model, we reveal rich electronic structures tuned by the ratio of hopping parameters, ranging from the band insulator to the unconventional gapless semiconductor. Remarkably, the unconventional gapless semiconductor is characterized by a flat band at the Fermi level. Further, the density functional theory calculations for candidate materials reveal that the characteristic electronic structures can be realized by designated chemisorption or chemical substitution on graphene and silicene, and that the electronic structure near the Fermi level is tunable by the choice of the atomic species of adsorbed atoms. Our results open the way to search exotic electronic structures and their functionalities induced by an extended martini lattice.