Poor Man's Approach to Exploring the Electronic Structures in Transition-Metal Oxides

In transition metal oxides (TMOs), the interactions among electronic spins, charges and orbitals account for the exotic properties such as metal-insulator transition, high-temperature superconductivity and colossal magnetoresistance. However, decent angle-resolved photoemission spectroscopy (ARPES) data are still lacking in many "uncleavable" perovskite-structure TMOs, which hinders the comprehensive understanding of the emergent phenomena in these correlated materials. Here, we develop a new method to prepare clean surfaces of Nd_0.8Sr_0.2NiO₃ and La_0.7Ca_0.3MnO₃ thin films, and investigate their electronic structures to track the microscopic origin of the metal-insulator transitions in these two systems. Our method can be generalized to study the 4d and 5d TMOs.