Electronic structure, magnetic correlations, and superconducting pairing in the reduced Ruddlesden-Popper bilayer La 3 Ni 2 O 6 under pressure: Different role of d 3 z 2 - r 2 orbital compared with La 3 Ni 2 O 7
- Univ. of Tennessee, Knoxville, TN (United States)
- Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
The recent discovery of superconductivity in bilayer La3Ni2O7 (327-LNO) under pressure stimulated much interest in layered nickelates. However, superconductivity was not found in another bilayer nickelate system, La3Ni2O6 (326-LNO), even under pressure. To understand the similarities and differences between 326-LNO and 327-LNO, using density functional theory and the random phase approximation (RPA), we systematically investigate 326-LNO under pressure. The large crystal-field splitting between the eg orbitals caused by the missing apical oxygen moves the d3z2-r2 orbital farther away from the Fermi level, implying that the d3z2-r2 orbital plays a less important role in 326-LNO than in 327-LNO. This also results in a smaller bandwidth for the dx2-y2 orbital and a reduced energy gap for the bonding-antibonding splitting of the d3z2-r2 orbital in 326-LNO, as compared to 327-LNO. Moreover, the in-plane hybridization between the dx2-y2 and d3z2-r2 orbitals is found to be small in 326-LNO, while it is much stronger in 327-LNO. Furthermore, the low-spin ferromagnetic state is found to be the likely ground state in 326-LNO under high pressure. The weak interlayer coupling suggests that s±-wave pairing is unlikely in 326-LNO. The robust in-plane ferromagnetic coupling also suggests that d-wave superconductivity, which is usually caused by antiferromagnetic fluctuations of the dx2-y2 orbital, is also unlikely in 326-LNO. These conclusions are supported by our many-body RPA calculations of the pairing behavior. Additionally, contrasting with the cuprates, for the bilayer cuprate HgBa2CaCu2O6, we find a strong self-doping effect of the dx2-y2 orbital under pressure, with the charge of Cu being reduced by approximately 0.13 electrons from 0 GPa to 25 GPa. In contrast, we do not observe such a change in the electronic density in 326-LNO under pressure, establishing another important difference between the nickelates and the cuprates.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES). Materials Sciences & Engineering Division (MSE)
- Grant/Contract Number:
- AC05-00OR22725
- OSTI ID:
- 2301636
- Alternate ID(s):
- OSTI ID: 2474069
- Journal Information:
- Physical Review. B, Journal Name: Physical Review. B Journal Issue: 4 Vol. 109; ISSN 2469-9950
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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