Orbital-dependent electron correlation in double-layer nickelate La3Ni2O7
Jiangang Yang, Hualei Sun, Xunwu Hu, Yuyang Xie, Taimin Miao, Hailan Luo, Hao Chen, Bo Liang, Wenpei Zhu, Gexing Qu, Cui-Qun Chen, Mengwu Huo, Yaobo Huang, Shenjin Zhang, Fengfeng Zhang, Feng Yang, Zhimin Wang, Qinjun Peng, Hanqing Mao, Guodong Liu, Zuyan Xu, Tian Qian, Dao‐Xin Yao, Meng Wang, Lin Zhao, Xingjiang Zhou
Abstract
Abstract The latest discovery of high temperature superconductivity near 80 K in La 3 Ni 2 O 7 under high pressure has attracted much attention. Many proposals are put forth to understand the origin of superconductivity. The determination of electronic structures is a prerequisite to establish theories to understand superconductivity in nickelates but is still lacking. Here we report our direct measurement of the electronic structures of La 3 Ni 2 O 7 by high-resolution angle-resolved photoemission spectroscopy. The Fermi surface and band structures of La 3 Ni 2 O 7 are observed and compared with the band structure calculations. Strong electron correlations are revealed which are orbital- and momentum-dependent. A flat band is formed from the Ni-3d $${}_{{z}^{2}}$$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mrow/><mml:mrow><mml:msup><mml:mrow><mml:mi>z</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:msub></mml:math> orbitals around the zone corner which is ~ 50 meV below the Fermi level and exhibits the strongest electron correlation. In many theoretical proposals, this band is expected to play the dominant role in generating superconductivity in La 3 Ni 2 O 7 . Our observations provide key experimental information to understand the electronic structure and origin of high temperature superconductivity in La 3 Ni 2 O 7 .