  Two-dimensional (2D) Dirac cone materials exhibit linear energy dispersion at
the Fermi level, where the effective masses of carriers are very close to zero
and the Fermi velocity is ultrahigh, only 2 ~ 3 orders of magnitude lower than
the light velocity. Such the Dirac cone materials have great promise in
high-performance electronic devices. Herein, we have employed the genetic
algorithms methods combining with first-principles calculations to propose a
new 2D anisotropic Dirac cone material, that is, orthorhombic boron phosphide
(BP) monolayer named as borophosphene. Molecular dynamics simulation and phonon
dispersion have been used to evaluate the dynamic and thermal stability of
borophosphene. Because of the unique arrangements of B-B and P-P dimers, the
mechanical and electronic properties are highly anisotropic. Of great interest
is that the Dirac cone of the borophosphene is robust, independent of in-plane
biaxial and uniaxial strains, and can also be observed in its one-dimensional
(1D) zigzag nanoribbons and armchair nanotubes. The Fermi velocities are ~ 105
m/s, the same order of magnitude with that of graphene. By using a
tight-binding model, the origin of the Dirac cone of borophosphene is analyzed.
Moreover, a unique feature of self-doping can be induced by the in-plane
biaxial and uniaxial strains of borophosphene and the Curvature effect of
nanotubes, which is great beneficial to realizing high speed carriers (holes).
Our results suggest that the borophosphene holds a great promise in
high-performance electronic devices, which could promote the experimental and
theoretical studies to further explore the potential applications of other 2D
Dirac cone sheets.
