Electronic properties of boron based 2D materials

Date: 11 June 2019

Venue: Campus Groenenborger, Building U, Room 244 - Groenenborgerlaan 171 - 2020 Antwerpen

Time: 4:00 PM - 5:00 PM

Organization / co-organization: CMT

Short description: CMT lecture presented by Mohammad Nakhaee, University of Damghan, Iran

Using simplified linear combination of atomic orbitals method in combination with first-principles calculations, we constructed a tight-binding (TB) model in the two-centre approximation for few dimensional boron based structures ie. borophene, hydrogenated borophene (borophane) and bilayer borophene. The Slater and Koster approach is applied to calculate the TB Hamiltonian of these systems. We obtain expressions for the Hamiltonian and overlap matrix elements between different orbitals for the different atoms and present the SK coefficients in a nonorthogonal basis set. An anisotropic Dirac cone is found in the band structure of borophane for witch we derive a Dirac low-energy Hamiltonian and compare the Fermi velocities with that of graphene. Concerning bilayer hexagonal borophene, we investigated its electronic band structure and found that it is a Dirac material which exhibits a nodal line. We constructed an effective four-band model Hamiltonian to describe the spectrum near the nodal line. This Hamiltonian can be used as a new platform to study the new properties of nodal line semimetals. We found that the nodal line is created by edge states and is very robust against perturbations and impurities. Breaking symmetries can split the nodal line, but cannot open a gap. 

1) Tight-binding model for borophene and borophane, M. Nakhaee, S. A. Ketabi, and F. M. Peeters, Phys. Rev. B 97, 125424 (2018).
2) Dirac nodal line in bilayer borophene: Tight-binding model and low-energy effective Hamiltonian, M. Nakhaee, S. A. Ketabi, and F. M. Peeters, Phys. Rev. B 98, 115413 (2018).

Contact email: lucian.covaci@uantwerpen.be

Link: http://cmt.uantwerpen.be