Metal-to-insulator transition in platinum group compounds

The metal-to-insulator transition (MIT) as usually achieved in 3d-orbital transitional metal (TM) compounds opens up a new paradigm in correlated electronics via triggering abrupt variations in their transportation properties. Compared to such 3d-orbital TM compounds, the MIT within the platinum group (Pg) element compounds based on the 4d- and 5d-orbital configurations is more complicated, owing to their elevation in the spin–orbit coupling and meanwhile weakened intra-atomic Coulomb repulsions. This brings in a new freedom to regulate the balance in their metallic or semiconductive orbital configurations, while their MIT properties can be potentially combined with their spintronic properties to enable new electronic applications. Herein, we review the electronic transport and MIT behaviors within the existing family of Pg-containing compounds, particularly those showing first-order MIT behaviors that can be useful in correlated electronics. It is also hoped that summarizing the presently reported Pg-containing MIT compounds will lead to the discovery of more new material families and/or new mechanisms associated with the Pg-containing compounds showing MIT properties.