Metallic nature of T-graphene sheet and nanotubes

The band structure, density of states (DOS), and Pauli magnetic susceptibility (PMS) of T-graphene nanotubes (TGNTs) with varying chiralities and diameters are investigated using the tight-binding Hamiltonian model and Green's function formalism. We analyze two edge types: zigzag (zTGNT) and armchair (aTGNT). Our findings reveal that both zTGNTs and aTGNTs exhibit metallic behavior regardless of diameter. Notably, aTGNTs feature Dirac points in their band structure, with their abundance increasing with nanotube diameter. As compared to graphene, when the diameter of the nanotube increases, aTGNTs reveal more Dirac points at the Fermi level. Additionally, increasing the diameter leads to the emergence of additional sub-bands in the band structure and van-Hove singularities in the DOS diagrams. Consequently, the PMS curves exhibit a crossover, dividing into distinct regimes at varying temperatures. The metallic properties of both TGNT types are apparent in the PMS curves, attributed to the proportional relationship between PMS and DOS. Furthermore, the DOS curves converge towards monolayer behavior as the TGNT diameter increases significantly.