Evolution of the charge density wave order on the two-dimensional hexagonal lattice

• Published in: Journal of magnetism and magnetic materials 2017-10, Vol.440, p.104-107
• Main Authors: Litak, Grzegorz, Wysokiński, Karol Izydor
• Format: Article
• Language: English
• Subjects: Bulk density; Carrier density; Charge density; Crystals; Fermi surfaces; Hexagonal lattice; Magnetism; Niobium; Physical properties; Stability; Symmetry; Transition temperature
• ISSN: 0304-8853; 1873-4766
• DOI: 10.1016/j.jmmm.2016.12.042

Experimental data on the monolayer niobium diselenide show that the single band crosses the Fermi energy. This is in striking contrast to the bulk systems in which at least three bands contribute to the Fermi surface of the material. Together with the fact that the charge density wave (CDW) transition temperature Tc of a bulk system and of a single layer are the same one concludes that it should allow description of the two dimensional system by a single band in the tight-binding approximation. We analyse the development of CDW order of triangular symmetry in two-dimensional lattice of hexagonal symmetry. We assume the existence of four sublattices and calculate the resulting density of states and the formation of CDW gap for systems with varying carrier concentration. The mechanism of CDW instability, most probably related to the strong electron-phonon coupling in the material, is modeled by the local attractive interaction U of the same strength on all sites. •The CDW order of triangular symmetry in 2d hexagonal lattice is analysed.•Four sub-lattices are assumed and the resulting density of states calculated.•The formation of CDW gap for systems with varying carrier concentration is studied.•Local attractive interaction U is assumed to be responsible for CDW instability.