The electronic structure of palladium on magnetoelectric Cr₂O₃(0001)

The band structure of ultrathin Pd(111) thin films grown on the Cr₂O₃(0001) surface was studied by angule-resolved photoemission spectroscopy (ARPES) combined with first-principles calculations. The Cr₂O₃(0001) interface and the expanded Pd lattice constant appears to significantly affect the occupied band structure of an ultrathin palladium film. A characteristic band splitting is seen in the experimental occupied electronic structure, forming a hexagonal pattern approximately half-way from theΓ¯point to the surface Brillouin zone boundary. The ARPES spectrum near the Fermi level is reproduced by the first-principles simulation for a Pd monolayer (ML) placed on the Cr-terminated Cr₂O₃surface with the energetically favorable lateral stacking. In this configuration, the Pd bands inside the Cr₂O₃band gap have a significant, momentum-dependent exchange splitting, which matches with the experimentally observed band splitting. The experimental band structure shows a band with an electron effective mass close to the free electron mass, neglecting mass enhancement effects close to the Fermi level. From the hybridization of the Pd ML with the Cr₂O₃(0001) substrate, a hole band with a mass of -0.48 ± 0.02 is identified.