Enhanced anisotropic electrical conductivity of perturbed monolayer ß12-borophene.

ß12-Borophene is a perfect planar nanolattice comprising of massless Dirac fermions and massless/massive triplet fermions considering the inversion symmetry lattice model. In this paper, a detailed study of the electric field and the effects of low concentrations of impurities on the electronic phase and the electrical conductivity of ß12-borophene is presented. As a direct manner to judge the electronic features of pristine and perturbed monolayer ß12-borophene, the five-band tight-binding Hamiltonian model, the T-matrix theory, the linear response theory, and the Green's function approach are investigated. Our investigation reveals that the massless Dirac and triplet fermions become massive when an electric field is applied. Also, we found out that the electric current and eventually the electrical conductivity are not the same along different directions and an enhancement of around 18.53% (15.38%) for the x-direction (in-plane) component is observed at a certain thermal energy. Furthermore, the metal-to-semiconductor electronic phase transition in the presence of different impurity atoms results in a 197.16% (198.23%) enhancement in x- (in-plane-) component of electrical conductivity. The results provide a basis of designing novel electronic devices based on ß12-borophene.

Strain engineering of optical activity in phosphorene.

Optical activity is one of the most fascinating fields in current physics. The strong anisotropic feature in monolayer phosphorene leads to the emergence of non-trivial optoelectronic physics. This paper is devoted to a detailed analysis of strain effects on the optical activity of phosphorene ranging from low-optical-field to high-optical-field. To do so, a numerical study of the two-band tight-binding model is accomplished using the Harrison rule and the linear response theory. Although the transparency of phosphorene confirms at all frequencies independent of the strain modulus and direction, on average, from low- to high-optical-field limit, the polarization of the reflected wave at critical strains becomes circular and the ellipse axis tends to a rotation of 180°. It is found that the maximum absorption takes place at high-energy transitions, which quantitatively depends strongly on the strain modulus and direction. Furthermore, a detailed investigation of compressive and tensile strains results in the dominant contribution of the in-plane compressive and out-of-plane tensile strains to the reflected/transmitted light for low- and intermediate-optical-field ranges, whilst both contribute for the high-optical-field limit. However, overall, in-plane compressive and out-of-plane tensile strains come in to play a role in the absorption spectra. Thereby, the quality of the determined reflection, transmission and absorption waves depends on the regarded regime of the optical field, strain modulus, and strain orientation. These findings if sufficient can be performed and/or tuned experimentally, and a vast number of phosphorene-based optoelectronic devices can be achieved.