Unveiling Strong Ion-Electron-Lattice Coupling and Electronic Antidoping in Hydrogenated Perovskite Nickelate.

Abstract

Despite being highly promising for applications in emergent electronic devices, decoding both the ion-electron-lattice coupling in correlated materials at the atomic scale and the electronic band structure remains a big challenge due to the strong and complex correlation among these degrees of freedom. Here, taking an epitaxial thin film of perovskite nickelate NdNiO₃ as a model system, hydrogen-ion-induced giant lattice distortion and enhanced NiO₆ octahedra tilting/rotation are demonstrated, which leads to a new robust hydrogenated HNdNiO₃ phase with lattice expansion larger than 10% on a series of substrates. Moreover, under the effect of ion-electron synergistic doping, it is found that the proposed electronic antidoping, i.e., the doped electrons mainly fill the ground-state oxygen 2p holes instead of changing the Ni oxidation state from Ni³⁺ to Ni²⁺ , dominates the metal-insulator transition. Meanwhile, lattice modification with enhanced Ni-O-Ni bond tilting or rotation mainly modifies the orbital density of states near the Fermi level. Last, by electric-field-controlled hydrogen-ion intercalation and its strong coupling to the lattice and electron charge, selective micrometer-scale patterns with distinct structural and electronic states are fabricated. The results provide direct evidence for a strong ion-electron-lattice coupling in correlated physics and exhibit its potential applications in designing novel materials and devices.