RCQM/FCMP: Qimiao Si: High temperature superconductivity in bilayer nickelates and beyond

Tuesday, Nov./18/2025, 2:00 PM to 3:00 PM (Houston)
Speaker: Qimiao Si
Institution: Rice University

Title: High temperature superconductivity in bilayer nickelates and beyond

Abstract: The discovery of superconductivity under pressure with a transition temperature of 80 K in the bilayer nickelate compound La3Ni2O7 [9] has generated considerable excitement. The recent extension of the phenomena to ambient conditions has further amplified the interest in the field. Some of the central questions concern the roles of electron correlations and multiple active orbitals. In this talk, I will introduce these systems in the broader context of correlated superconductors that develop out of bad metals, including the infinite layer nickelates and the even more extensively studied iron-based superconductors. I will then address the role of electron correlations, with a particular emphasis on orbital-selective behavior, for both the normal and superconducting states. I will show how such effects influence the low-energy electronic structure [1,2] and electronic dynamics [2], and how they drive the superconducting pairing through both interlayer and intralayer exchange pathways [3]. Our theoretical findings, especially on the orbital-selective effects, compare well with experimental results, including spectroscopic measurements that shed light on the underlying correlation effects in the normal state [4,5] as well as the measurements on the pairing gap structure in thin films of the bilayer system at ambient conditions [6,7]. Finally, I will touch upon related systems within the broader family of multilayer Ruddlesden-Popper nickelates [8].

Reference:
[1] Z. Liao et al, Phys. Rev. B 108, 214522 (2023);
[2] Z. Liao et al, arXiv:2412.21019;
[3] G. Duan et al., arXiv:2502.09195
[4] J. Yang et al., Nat. Comm. 15, 4373 (2024);
[5] Z. Liu et al, Nat. Comm. 15, 7570 (2024)
[6] J. Shen et al., arXiv:2502.17831
[7] S. Fan et al., arXiv:2506.01788
[8] K-S Lin, Y. Wang, Z. G. Liao, R. Yu, QS, to be published (2025).
[9] H. Sun et al, Nature 621, 493 (2023)