Nature and Role of Interstitial States in Infinite-Layer Nickelate Superconductors

by Prof. Gang Li（李刚） (ShanghaiTech University)

Wednesday 3 Jun 2026, 10:00 → 11:00 Asia/Shanghai

Tsung-Dao Lee Institute/N4F-N400 - meeting room (Tsung-Dao Lee Institute)

Host: Prof. Ruidan Zhong  

Venue: TDLI Meeting Room N400

Tencent Meeting link: https://meeting.tencent.com/dm/IqfefDVwM4aW

 Meeting ID: 967837492, no password

 

Abstract:

Infinite-layer nickelates are widely considered to share key characteristics with cuprate high-temperature superconductors, including similar valence states and fundamental structural units. However, unlike cuprates, nickelates possess an additional electron pocket at the A-point of the Brillouin zone, the nature and role of which remain unclear. The debate over this electron pocket is central to determining whether these emerging superconductors are best described by a single-band or multi-band model and has implications for their pairing symmetry. In this talk, we employ quantum topological chemistry theory to link this interstitial state to an obstructed charge center. Our analysis reveals that the interstitial state exhibits definite s-orbital symmetry and occupies a fixed position in the crystal structure—both properties dictated by its obstructed character. We further demonstrate that while the occupation of this interstitial state stabilizes the crystal structure and preserves the Ni–d9 valence configuration, it does not appear to enhance superconductivity or contribute additional electron screening. By further tracing the hole distribution, we provide a picture supporting the interstitial state as a charge donor which enhancing band renormalization of the Ni–3d x2-y2 orbital by increasing its electron occupancy. These results reinforce the view that superconductivity in infinite-layer nickelates is predominantly governed by a single-band mechanism.

 

Reference:

1. Hongbin Qu, Guang-Ming Zhang, and Gang Li, arXiv:2507.10364
2. Gang Li, Guang-Ming Zhang, et al. (to be submitted)

 

Biography:

Gang Li is a tenured associate professor and researcher at ShanghaiTech University, selected for Shanghai Municipal and National Talent Programs. He received his Ph.D. from the University of Bonn, Germany, in 2009. He subsequently held postdoctoral positions at the University of Würzburg, Germany, and TU Wien, Austria, and served as a joint researcher in a major German national project. He joined ShanghaiTech University in February 2017. Dr. Li’s research focuses on computational and theoretical studies of strongly correlated electron materials and topological quantum materials. By extending and applying dynamical mean-field type many-body methods, he investigates various emergent quantum states in condensed matter, including quantum spin liquid states and unconventional superconductivity.