Frequency and orientation dependent conductivity of a semi-Dirac system

Abstract

The intra- and interband optical conductivities of a semi-Dirac system are determined. It was found that the conductivity in the linear direction is considerably stronger than the conductivity in the parabolic direction. For an electrical field applied along a non-principal axis, both the the longitudinal and transverse current are nonzero. Due to the anisotropy of the system, the transverse conductivity for an oblique applied field can exceed the longitudinal conductivity.

Optical properties of a semi-Dirac material

“…In this case, the material parameters m and v have dropped out as has the scattering rate √ Γ which appears in Eqs. (41) and (42) so that the remaining prefactor unit is simply e 2 /h. There are only small differences between these curves and the corresponding curves for graphene (not shown).…”

“…σ yy (T, µ, Ω) ≡ e 2 h mv 2 Γ σyy ( T , μ, Ω), (42) where any variable x ≡ x/Γ. For T = 0, the two functions σxx and σyy are universal functions of μ and Ω which can be plotted as a family of curves with label μ as a function of Ω.…”

“…7, we show our numerical results for μ = 0, 1, 2.5, 5 and 10, evaluated from Eqs. (41) and (42). The top frame is for σxx (µ, Ω) or σ xx (µ, Ω) normalized by e 2 h Γ mv 2 and the bottom frame is for σyy (µ, Ω) or σ yy (µ, Ω) in units of e 2 h mv 2 Γ .…”

“…Large differences between σ xx (Ω) and σ yy (Ω) imply that for an electric field orientated in an arbitrary direction with respect to the (x, y) axes, the conductivity will have a finite transverse, as well as, a longitudinal component. 42 This is in contrast to graphene which is isotropic. The anisotropy of the semi-Dirac model, which is not part of the pure Dirac case, has other consequences.…”

Anisotropic and tunable optical conductivity of a two-dimensional semi-Dirac system in the presence of elliptically polarized radiation

“…Several investigations of the electronic and optical properties of 2D SD systems have been carried out recently. In particular, the electronic, optoelectronic, and transport properties such as Floquet band structure [13,14], optical conductivity [15][16][17][18], dielectric function and plasmons [11], nonlinear response [19], and ballistic transport modulated by magnetic and electrical barriers [20] have been studied. It has been shown that the 2D SD system can transform from normal insulator to the Chern insulating phase under light irradiation with relatively high frequencies [21,22].…”