Electronic Properties of Graphyne and Graphdiyne in Tight-binding Model

Abstract

In this theoretical study, within the nearest neighbor tight-binding model, the density of states (DOS), Pauli magnetic susceptibility (PMS), and electronic heat capacity (EHC) of graphyne-like systems, i.e. α -, β -, γ -, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>6</mml:mn> <mml:mo>,</mml:mo> <mml:mn>6</mml:mn> <mml:mo>,</mml:mo> <mml:mn>12</mml:mn> </mml:math> -graphyne, and graphdiyne are calculated and the results are compared with that of a graphene monolayer. It is observed that α -, β - and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mn>6</mml:mn> <mml:mo>,</mml:mo> <mml:mn>6</mml:mn> <mml:mo>,</mml:mo> <mml:mn>12</mml:mn> </mml:math> -graphyne are semimetals with a zero bandgap similar to a graphene monolayer, while γ -graphyne and graphdiyne have no states around the Fermi level. In addition, the intra-bandgaps are seen in the DOS of graphyne structures and the van-Hove singularities in the DOS of all systems. These lead to the crossovers occurred in the PMS curves and the Schottky anomaly peaks in the EHC curves, which are divided into two low and high temperature regions. Also, it is found that close to the temperature of zero, the PMS and EHC of all semimetal systems are slightly higher than semiconducting systems. From the theoretical stand point, this phenomenon stems from the proportional relation of the PMS and EHC with DOS.