Structure Responsible for the Superconducting State in La3Ni2O7 at High-Pressure and Low-Temperature Conditions

Luhong Wang; Yan Li; Sheng-Yi Xie; Fuyang Liu; Hualei Sun; Chaoxin Huang; Yang Gao; Takeshi Nakagawa; Boyang Fu; Bo Dong; Zhenhui Cao; Runze Yu; Saori I Kawaguchi; Hirokazu Kadobayashi; Meng Wang; Changqing Jin; Ho-Kwang Mao; Haozhe Liu

doi:10.1021/jacs.3c13094

Structure Responsible for the Superconducting State in La₃Ni₂O₇ at High-Pressure and Low-Temperature Conditions

J Am Chem Soc. 2024 Mar 20;146(11):7506-7514. doi: 10.1021/jacs.3c13094. Epub 2024 Mar 8.

Authors

Luhong Wang¹, Yan Li², Sheng-Yi Xie³, Fuyang Liu⁴, Hualei Sun⁵, Chaoxin Huang⁶, Yang Gao⁴, Takeshi Nakagawa⁴, Boyang Fu⁷, Bo Dong⁸, Zhenhui Cao², Runze Yu⁴, Saori I Kawaguchi⁹, Hirokazu Kadobayashi⁹, Meng Wang⁶, Changqing Jin¹⁰, Ho-Kwang Mao^{11

4}, Haozhe Liu⁴

Affiliations

¹ Shanghai Key Laboratory of Material Frontiers Research in Extreme Environments, Shanghai Advanced Research in Physical Sciences, Shanghai 201203, China.
² State Key Lab of Superhard Materials, College of Physics, Jilin University, Changchun 130012, China.
³ School of Physics and Electronics, Hunan University, Changsha 410082, China.
⁴ Center for High Pressure Science & Technology Advanced Research, Beijing 100094, China.
⁵ School of Sciences, Sun Yat-Sen University, Guangzhou, Guangdong 510275, China.
⁶ Center for Neutron Science and Technology, Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices, School of Physics, Sun Yat-Sen University, Guangzhou, Guangdong 510275, China.
⁷ School of Materials and Energy, University of Electronic Science and Technology of China, Chengdu, Sichuan 611731, China.
⁸ Harbin Institute of Technology, Harbin 150001, China.
⁹ Japan Synchrotron Radiation Research Institute, SPring-8, Sayo-gun Hyogo 679-5198, Japan.
¹⁰ Beijing National Lab for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
¹¹ Shanghai Advanced Research in Physical Sciences, Shanghai 201203, China.

PMID: 38457476
DOI: 10.1021/jacs.3c13094

Abstract

Very recently, a new superconductor with T_c = 80 K has been reported in nickelate (La₃Ni₂O₇) at around 15-40 GPa conditions (Nature, 621, 493, 2023), which is the second type of unconventional superconductor, besides cuprates, with T_c above liquid nitrogen temperature. However, the phase diagram plotted in this report was mostly based on the transport measurement under low-temperature and high-pressure conditions, and the assumed corresponding X-ray diffraction (XRD) results were carried out at room temperature. This encouraged us to carry out in situ high-pressure and low-temperature synchrotron XRD experiments to determine which phase is responsible for the high T_c state. In addition to the phase transition from the orthorhombic Amam structure to the orthorhombic Fmmm structure, a tetragonal phase with the space group of I4/mmm was discovered when the sample was compressed to around 19 GPa at 40 K where the superconductivity takes place in La₃Ni₂O₇. The calculations based on this tetragonal structure reveal that the electronic states that approached the Fermi energy were mainly dominated by the e_g orbitals (3d_z² and 3d_x²-y²) of Ni atoms, which are located in the oxygen octahedral crystal field. The correlation between T_c and this structural evolution, especially Ni-O octahedra regularity and the in-plane Ni-O-Ni bonding angles, is analyzed. This work sheds new light to identify what is the most likely phase responsible for superconductivity in double-layered nickelate.