Frequency switchable correlated transports in perovskite rare-earth nickelates†
While electron correlations were previously recognized to result in direct current (DC) transportation properties beyond-conventional (e.g., metal-to-insulator transitions, bad metal, thermistors), their respective influences on the alternating current (AC) transport are largely overlooked. Herein, active regulation of the electronic functionalities of d-band correlated rare-earth nickelate (ReNiO3) thin films, by simply utilizing their electronic responses to AC-frequencies (fAC) is demonstrated. Assisted by temperature dependent near edge X-ray absorption fine structure analysis, positive temperature dependences in the Coulomb viscosity of ReNiO3 were discovered, which moderate their AC impedance (R′ + iR′′). Distinguished crosslinking among R′–fAC measured in nearby temperatures is observed that differs to conventional oxides. This enables active adjustability in correlated transports of ReNiO3, among NTCR-, TDelta- and PTCR-thermistors, via fAC from the electronic perspective without varying materials or device structures. Furthermore the TDelta–fAC relationship can be widely adjusted via the Re composition and interfacial strains. The AC-frequency sensitivity discovered in ReNiO3 leads the way to a new freedom in regulating and switching the device working states beyond the present semiconductor technologies. It opens up a new model for enriching novel electronic applications in automatic transmission, artificial intelligence in sensing temperatures or thermal perturbations.