Fig. 2: Magnetization measurement and magneto-infrared spectroscopy of EuCd2As2.
From: The discovery of three-dimensional Van Hove singularity
a Out-of-plane magnetic field dependence of magnetization at different temperatures. Denoted by the gray arrows, the magnetic ground state of EuCd2As2 is A-type AFM. When an out-of-plane magnetic field is applied, it undergoes spin canting and reaches magnetic saturation around 2 T at 2 K (dashed gray line). b Temperature evolution of magnetization indicating an antiferromagnetic transition. c and d False-color plot of relative reflectivity \({R}_{{B}}/{R}_{0}\) of EuCd2As2 at 8 K measured in NHMFL and ECNU, respectively. The intensity of optical features increases abruptly at the critical field \({B}_{{{{{{\rm{c}}}}}}} \, \approx \, 0.6\,{{{{{\rm{T}}}}}}\) (white arrow) in the spectrum from both setups. The blue and red arrows point out the energy evolution of \({{{{{{\rm{T}}}}}}}_{\alpha }\) and \({{{{{{\rm{T}}}}}}}_{\beta }\), respectively. e and f The comparison between magnetization and the energy of \({{{{{{\rm{T}}}}}}}_{\alpha },{{{{{{\rm{T}}}}}}}_{\beta }\). The blue and red squares denote the apparent energy of \({{{{{{\rm{T}}}}}}}_{\alpha }\) and \({{{{{{\rm{T}}}}}}}_{\beta }\). The energy error of \({{{{{{\rm{T}}}}}}}_{\beta }\) determined from the ECNU spectra is much smaller than the symbol size. The solid curves represent the linear scaling of magnetization with the scaling parameter labeled near the corresponding curves. It suggests that the continuous shift of the electronic bands originates from magnetization. Meanwhile, the magnetization increases smoothly around \({B}_{{{{{{\rm{c}}}}}}}\) in contrast to the abrupt enhancement of optical transitions. Hence, the electronic property of EuCd2As2 experiences sharp change while the Weyl band is continuously shifted by the external magnetic field.
