Temperature-dependent terahertz properties of carriers and phonons in the topological Dirac semimetal Cd3As2

As a three-dimensional (3D) analog of graphene, the cadmium arsenide $({\mathrm{Cd}}_{3}{\mathrm{As}}_{2})$ based topological Dirac semimetal has attracted enormous research interest recently. In this work, the temperature-dependent terahertz (THz) properties of ${\mathrm{Cd}}_{3}{\mathrm{As}}_{2}$ prepared epitaxially are investigated by using THz time-domain spectroscopy. In the regime of $1.5\ensuremath{\sim}300$ K, we obtain the optical conductivity of ${\mathrm{Cd}}_{3}{\mathrm{As}}_{2}$ and observe a remarkable phonon absorption peak in the range of $1.7\ensuremath{\sim}1.8$ THz. More importantly, it is demonstrated that the effects of weak electronic confinement and optical-phonon-limited behavior of carriers are dominated below and above $\ensuremath{\sim}60$ K, respectively. The weak electronic confinement can be attributed to the diffusive restoring current in polycrystalline grains of ${\mathrm{Cd}}_{3}{\mathrm{As}}_{2}$. Based on the Drude-Lorentz formula and the modified Drude-Smith formula, the temperature dependencies of the characteristic parameters are extracted to describe the carrier and phonon behaviors. These results not only can provide detailed knowledge of the THz response of epitaxially grown ${\mathrm{Cd}}_{3}{\mathrm{As}}_{2}$ depending on temperature but also may find applications in optoelectronic devices based on 3D Dirac semimetals.