Tuning the metal-insulator transition in NdNiO3 heterostructures


The metal-insulator transitions (MITs) in complex oxides are often precursors to exotic ground states such as high-temperature superconductivity, colossal magnetoresistance, and different types of charge-, spin- and orbital-ordered states. In this context, rare-earth nickelates (RNiO3, where R = rare-earth elements) can be viewed as model systems, which exhibit temperature-driven MITs. Novel routes to engineering and controlling the MIT in thin films and heterostructures of RNiO3 further offer the possibility to control the MIT with thickness via strain using different substrates. Here, we employed in situ pulsed laser deposition (PLD) and angle-resolved photoemission spectroscopy (ARPES) to investigate the mechanism of the metal-insulator transition (MIT) in NdNiO3 (NNO) thin films, grown on NdGaO3(110) and LaAlO3(100) substrates. In the metallic phase, we observe three-dimensional hole and electron Fermi surface (FS) pockets formed from strongly renormalized bands with well-defined quasiparticles. Upon cooling across the MIT in NNO/NGO sample, the quasiparticles lose coherence via a spectral weight transfer from near the Fermi level to localized states forming at higher binding energies. In the case of NNO/LAO, the bands are apparently shifted upward with an additional holelike pocket forming at the corner of the Brillouin zone. We find that the renormalization effects are strongly anisotropic and are stronger in NNO/NGO than NNO/LAO. Our study reveals that substrate-induced strain tunes the crystal field splitting, which changes the FS properties, nesting conditions, and spin-fluctuation strength, and thereby controls the MIT via the formation of an electronic order parameter.

Contact details: 

Dr. Rajendra S. Dhaka

Department of Physics