Investigation of optical properties of 3D Dirac materials*

3D Dirac semimetals are newly discovered topological materials that are characterized by Weyl nodes with double degeneracy in the bulk. The electronic bands are protected from gapping by crystal symmetries and touch at special points in the BZ zone. A Dirac semimetal band structure has been observed in with ARPES but the study of their electric-optical properties has yet to be further developed Here, we present spectral measurements on the 3D Dirac semimetal . Using FITR technics in reflectivity configuration, we have observed the electromagnetic response of the 3D Dirac material from the FIR up to the NIR frequency range in different electrical field polarization configuration. Our measurements reveal the presence of unusual collective excitations near the screened plasma frequency. We attribute these excitations as arising from the extra -term in the action of the electromagnetic field that originates from the chiral shift between the Weyl nodes. We will also present the optical response in an applied magnetic field.