Revealing 'plasmaron' feature in DySb by optical spectroscopy study

We report magnetic susceptibility, resistivity and optical spectroscopy study on single crystal sample DySb. It exhibits extremely large magnetoresistance (XMR), and a magnetic phase transition from paramagnetic (PM) to antiferromagnetic (AFM) state at about 10 K. A 'screened' plasma edge at about 4000 cm^-1 is revealed by optical measurement, which suggests that the material has a low carrier density. With decreasing temperature, the 'screened' plasma edge shows a blue shift, possibly due to a decrease of the effective mass of carriers. Notably, an anomalous temperature dependent midinfrared absorption feature is observed in the vicinity of the 'screened' plasma edge. In addition, it can be connected to the inflection point in the real part of the dielectric function [Formula: see text], the frequency of which exactly tracks the temperature dependent 'screened' plasma frequency. This phenomena can be explained by the appearance of a coupled electron-plasmon 'plasmaron' feature.