Improved conduction and orbital polarization in ultrathin LaNiO3 sublayer by modulating octahedron rotation in LaNiO3/CaTiO3 superlattices

Wenxiao Shi; Jing Zhang; Bowen Yu; Jie Zheng; Mengqin Wang; Zhe Li; Jingying Zheng; Banggui Liu; Yunzhong Chen; Fengxia Hu; Baogen Shen; Yuansha Chen; Jirong Sun

doi:10.1038/s41467-024-54311-0

Improved conduction and orbital polarization in ultrathin LaNiO₃ sublayer by modulating octahedron rotation in LaNiO₃/CaTiO₃ superlattices

Nat Commun. 2024 Nov 15;15(1):9931. doi: 10.1038/s41467-024-54311-0.

Authors

Wenxiao Shi^#^{1

2}, Jing Zhang^#³, Bowen Yu^#^{1

2}, Jie Zheng^{1

2}, Mengqin Wang^{1

2}, Zhe Li^{1

2}, Jingying Zheng⁴, Banggui Liu^{5

6}, Yunzhong Chen^{1

2}, Fengxia Hu^{1

2}, Baogen Shen^{1

2

7}, Yuansha Chen^{8

9}, Jirong Sun^{10

11

12}

Affiliations

¹ Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China.
² School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China.
³ Songshan Lake Materials Laboratory, Dongguan, Guangdong, China.
⁴ College of Materials Science & Engineering, Fuzhou University, Fuzhou, China.
⁵ Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China. [email protected].
⁶ School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China. [email protected].
⁷ Ningbo Institute of Materials Technology & Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang, China.
⁸ Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China. [email protected].
⁹ School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China. [email protected].
¹⁰ Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing, China. [email protected].
¹¹ School of Physical Sciences, University of Chinese Academy of Sciences, Beijing, China. [email protected].
¹² School of Materials Science & Engineering, Taiyuan University of Science and Technology, Taiyuan, China. [email protected].

^# Contributed equally.

Abstract

Artificial oxide heterostructures have provided promising platforms for the exploration of emergent quantum phases with extraordinary properties. Here, we demonstrate an approach to stabilize a distinct oxygen octahedron rotation (OOR) characterized by $a^{-} a^{-} c^{+}$ in the ultrathin LaNiO₃ sublayers of the LaNiO₃/CaTiO₃ superlattices. Unlike the $a^{-} a^{-} c^{-}$ OOR in the LaNiO₃ bare film, the $a^{-} a^{-} c^{+}$ OOR favors high conductivity, driving the LaNiO₃ sublayer to a metallic state of ~100 K even when the layer thickness is as thin as 2 unit cells (u.c.). Simultaneously, strongly preferred occupation of $d_{x^{2} - y^{2}}$ orbital is achieved in LaNiO₃ sublayers. The largest change of occupancy is as high as 35%, observed in the 2 u.c.-thick LaNiO₃ sublayers sandwiched between 4 u.c.-thick CaTiO₃ sublayers. X-ray absorption spectra indicate that the $a^{-} a^{-} c^{+}$ OOR pattern of LaNiO₃ achieved in the LaNiO₃/CaTiO₃ heterostructures has significantly enhanced the Ni-3d/O-2p hybridization, stabilizing the metallic phase in ultrathin LaNiO₃ sublayers. The present work demonstrates that modulating the mode of OOR through heteroepitaxial synthesis can modify the orbital-lattice correlations in correlated perovskite oxides, revealing hidden properties of the materials.