Interband optical conductivity of [001]-oriented Dirac semimetal Cd3As2

Abstract

We measured the optical reflectivity of [001]-oriented n-doped Cd\(_{3}\)As\(_{2}\) in a broad frequency range (50 - 22000 cm\(^{-1}\)) for temperatures from 10 to 300 K. The optical conductivity, \(\sigma(\omega) = \sigma_{1}(\omega) + i\sigma_{2}(\omega)\), is isotropic within the (001)-plane, its real part follows a power law, \(\sigma_{1}(\omega) \propto \omega^{1.65}\), in a large interval from 2000 to 8000 cm\(^{-1}\). This behavior is caused by interband transitions between two Dirac bands, which are effectively described by a sub-linear dispersion relation, \(E(k) \propto \lvert k \rvert ^{0.6}\). The momentum-averaged Fermi velocity of the carriers in these bands is energy dependent and ranges from \(1.2 \times 10^{5}\) to \(3 \times 10^{5}\) m/s, depending on the distance from the Dirac points. We show that an optical-conductivity model, which includes the self-energy effects, provides an adequate description of the experimental interband \(\sigma_{1}(\omega)\).