Semimetallic nature of and magnetic polarons in EuB6 studied using angle-resolved photoemission spectroscopy

Abstract

Temperature-dependent angle-resolved photoemission spectroscopy (ARPES) was carried out on single-crystalline EuB6 samples. By measuring ARPES spectra in an extended Brillouin zone, we clearly observed a B 2p hole pocket centered at the X point, thus proving the semimetallic nature of EuB6. Below the Curie temperature T-C, ARPES spectra show two B 2p bands of which separation is due to an exchange interaction between local Eu 4f and itinerant B 2p electrons. The exchange splitting becomes smaller as the temperature increases and disappears well above T-C. Additionally, a diffuse structure near the Fermi level survives at temperatures just above T-C. Such behavior is well described by using Monte Carlo simulations of a Kondo-lattice model, thus supporting the formation of magnetic polarons in EuB6, which accounts for the resistivity upturn slightly above T-C as the temperature is lowered.