Nature of the metal-insulator transition in few-unit-cell-thick LaNiO3 films

M Golalikhani; Q Lei; R U Chandrasena; L Kasaei; H Park; J Bai; P Orgiani; J Ciston; G E Sterbinsky; D A Arena; P Shafer; E Arenholz; B A Davidson; A J Millis; A X Gray; X X Xi

doi:10.1038/s41467-018-04546-5

Nature of the metal-insulator transition in few-unit-cell-thick LaNiO₃ films

Nat Commun. 2018 Jun 7;9(1):2206. doi: 10.1038/s41467-018-04546-5.

Authors

M Golalikhani¹, Q Lei², R U Chandrasena^{2

3}, L Kasaei², H Park^{4

5}, J Bai⁶, P Orgiani^{7

8}, J Ciston⁹, G E Sterbinsky¹⁰, D A Arena¹¹, P Shafer¹², E Arenholz¹², B A Davidson^{2

8}, A J Millis^{13

14}, A X Gray^{2

3}, X X Xi^{15

16}

Affiliations

¹ Department of Physics, Temple University, Philadelphia, PA, 19122, USA. maryam@temple.edu.
² Department of Physics, Temple University, Philadelphia, PA, 19122, USA.
³ Temple Materials Institute, Temple University, Philadelphia, PA, 19122, USA.
⁴ Department of Physics, University of Illinois at Chicago, Chicago, IL, 60607, USA.
⁵ Materials Science Division, Argonne National Laboratory, Argonne, IL, 60439, USA.
⁶ National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, NY, 11973, USA.
⁷ CNR-SPIN, UOS Salerno, 84084, Fisciano, Italy.
⁸ CNR-IOM, TASC Laboratory in Area Science Park, 34139, Trieste, Italy.
⁹ National Center for Electron Microscopy Facility, Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
¹⁰ Advanced Photon Source, Argonne National Laboratory, Argonne, IL, 60439, USA.
¹¹ Department of Physics, University of South Florida, Tampa, FL, 33620, USA.
¹² Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
¹³ Department of Physics, Columbia University, New York, NY, 10027, USA.
¹⁴ Center for Computational Quantum Physics, The Flatiron Institute, New York, NY, 10010, USA.
¹⁵ Department of Physics, Temple University, Philadelphia, PA, 19122, USA. xiaoxing@temple.edu.
¹⁶ Temple Materials Institute, Temple University, Philadelphia, PA, 19122, USA. xiaoxing@temple.edu.

Abstract

The nature of the metal-insulator transition in thin films and superlattices of LaNiO₃ only a few unit cells in thickness remains elusive despite tremendous effort. Quantum confinement and epitaxial strain have been evoked as the mechanisms, although other factors such as growth-induced disorder, cation non-stoichiometry, oxygen vacancies, and substrate-film interface quality may also affect the observable properties of ultrathin films. Here we report results obtained for near-ideal LaNiO₃ films with different thicknesses and terminations grown by atomic layer-by-layer laser molecular beam epitaxy on LaAlO₃ substrates. We find that the room-temperature metallic behavior persists until the film thickness is reduced to an unprecedentedly small 1.5 unit cells (NiO₂ termination). Electronic structure measurements using X-ray absorption spectroscopy and first-principles calculation suggest that oxygen vacancies existing in the films also contribute to the metal-insulator transition.

Publication types

Research Support, U.S. Gov't, Non-P.H.S.