Temperature dependent optical conductivity of RAlGe (R = La, Ce, Pr) Weyl semimetal

Topological materials are new types of quantum materials on which phases of matter are classified by surface states produced by the topology of the bulk band structure. Among them, topological Weyl semimetals have gained popularity for exhibiting quantum anomalies such as a topological Fermi arc and chiral anomaly from Weyl fermions. Recent material survey extends to magnetic semimetals, especially rare-earth based magnetic non-centrosymmetric Weyl semimetals showing a rich topological tunability of Weyl fermions at the low-energy band structures. Here, we report a strong mid-far infrared frequency dependence of the optical conductivity in RAlGe (R = La, Ce, Pr) Weyl semimetal. The optical conductivity is extracted by applying complex Kramers-Kronig analysis on reflection spectrums ranging from a few eV to 1eV. The rare-earth compounds RAlGe host either type-I and/or type-II Weyl fermions depending on the rare-earth ion. LaAlGe is nonmagnetic while CeAlGe and PrAlGe are ferromagnetic with different easy axes. A comparative study of the optical conductivity on these three compounds reveals distinct infrared spectroscopic features of different types of Weyl semimetals.