Carbon nanotube array as a van der Waals two-dimensional hyperbolic material

Abstract

We use an ab-initio approach to design and study a novel two-dimensional material -a planar array of carbon nanotubes separated by an optimal distance defined by the van der Waals interaction. We show that the energy spectrum for an array of quasi-metallic nanotubes is described by a strongly anisotropic hyperbolic dispersion and formulate a model low-energy Hamiltonian for its semi-analytical treatment. Periodic-potential-induced lifting of the valley degeneracy for an array of zigzag narrow-gap nanotubes leads to the band gap collapse. In contrast, the band gap is opened in an array of gapless armchair tubes. These unusual spectra, marked by pronounced van Hove singularities in the low-energy density of states, open the opportunity for interesting physical effects and prospective optoelectronic applications. arXiv:1904.06372v4 [cond-mat.mes-hall]

Electric field assisted alignment of monoatomic carbon chains

“…Therefore the interaction between parallel chains is expected to be weaker than the interactions between neighboring carbon atoms in a chain. Thus, we conclude that the force responsible for the formation of a carbyne bundle is likely to be the Van der Waals force 7,13,19,20 .…”

Optical absorption in two-dimensional materials with tilted Dirac cones

“…Consequently, the results of Eqs. ( 7) and (8) show that the transition rate W θ (ν, q) at wavevector q given in Eq. ( 4) is also independent of the tilt parameter (γ) (from type-I to II to III) and depends only on the Fermi velocity anisotropy factor (η).…”

“…Beyond type-I Dirac cones there exists DSMs with open Fermi surfaces: critically tilted (type-III) Dirac cones with parabolic Fermi surfaces and super-critically tilted (type-II) Dirac cones with hyperbolic Fermi surfaces. There exists a variety of candidate tilted Dirac cones [2] in different systems such as: partially hydrogenated graphene [3], warped graphene [4], organic conductor α-(BEDT-TTF) 2 I 3 [5], 8-P mmn Borophene [6,7], planar arrays of carbon nanotubes [8], artificial graphenes [9,10] and others [11][12][13][14][15][16][17].…”

Quasi-exact solutions for guided modes in two-dimensional materials with tilted Dirac cones

“…In extension to the well-known case of graphene, Dirac cones can in general possess valley-dependent tilt 23 . There are only a handful of 2D electronic systems that have been predicted to host these tilted cones 24 – 33 , one of which is 8- Pmmn borophene 23 , 34 , which has attracted considerable attention. In general, boron-based nanomaterials are a growing field of interest 35 – 37 ; indeed, exploring the tilt of 2D Dirac cones in the context of 8- Pmmn borophene has recently led to a plethora of theoretical works spanning many fields of research 38 – 84 from optics to transport, and many more; for a comprehensive review, see Ref.…”