Worm-graphene: A two-dimensional orthorhombic carbon semimetal with massless Dirac fermion

Low energy Dirac material of carbon other than graphene has always enthralled researchers for their unique properties. Based on first-principles calculation we propose a carbon polymorph identified by the predominance of a Dirac cone in the contiguity of the Fermi level in the Two-dimensional domain. Moreover, the stable pristine structure known as Worm-graphene involves six non-equivalent carbon atoms to effectuate an atomic density 0.372 atoms/& ANGS;(2) which is close to graphene. The Dirac cone exhibits anisotropic Fermi velocity with 6.85 x 10(5) m/s being its highest value. Besides, simple tight-binding Hamiltonian can be formulated to express the origin of the Dirac cone. Interestingly, strain resilient semimetallic behavior with robust Dirac cone of the system can be validated within 10% compressive to 10% tensile strain. Further, the material also possesses anisotropic In-plane Young's modulus unlike graphene. Appreciable degree of spin-polarization due to monovacancy defect can be established from induced magnetic moment. Additionally, nanotubes rolled-up from this sheet can be both semimetallic or semiconducting depending on the rolling direction. Free standing Worm-graphene sheet shows strikingly different optical response compared to graphene. Two collective oscillations of the system within visible range happen to be the distinguishing trait.

Automated summary

Low energy Dirac material of carbon other than graphene has attracted researchers for their unique properties. Based on first-principles calculation, a carbon polymorph with a predominant Dirac cone near the Fermi level in the two-dimensional domain is proposed. The stable pristine structure, called Worm-graphene, has a similar atomic density to graphene and exhibits anisotropic properties. The material shows strain resilient semimetallic behavior with a robust Dirac cone, and the rolled-up nanotubes can be either semimetallic or semiconducting depending on the rolling direction. Additionally, the free-standing Worm-graphene sheet has a significantly different optical response compared to graphene.