Nickelate superconductivity: a new playground for unconventional superconductors

Date

Jun 30, 2025

Time

11:00 AM - 12:00 PM

Speaker

Prof. Hai Wu Wen

Affiliation

Nanjing University, China

Language

en

Main Topic

Materialien

Host

Rita Taubert

Description

The discovery of high-temperature superconductivity in nickelate system has stimulated tremendous interest in the community [1,2]. Among the nickelate superconductors, two typical systems have attracted the most attention, namely the infinite layer RE1-xSrxNiO2 with Tc reaching about 40 K, and the bilayer system La3Ni2O7 with Tc above 90 K. In this talk I will report the progress in this rapidly developing field. Then I will report some progress in our group. We have synthesized bulk samples of the infinite layer system bulk RE1-xSrxNiO2 (RE = Nd, Sm) and found no superconductivity [3]. Detailed and careful TEM measurements unravel the puzzles why the bulk samples are not superconductive [4]. We have also carried out single particle tunneling measurement on the nickelate superconducting thin film Nd1-xSrxNiO2, a dominant V-shape spectrum (with a d-wave gap around 4 meV) was discovered [5], which is mixed with a passive s-wave component (~2meV). Combining with theoretical calculations, we attribute the dominant d-wave gap to the pairing potential of the orbital. Recently, we have also succeeded in growing the strained thin films of La2PrNi2O7 with Tconset = 41.5 K. Tunneling spectra are successfully measured on the terraces after we removed the surface layer and expose the superconducting layer by using the tip-excavation technique. The spectrum shows a two-gap structure with delta1 ~ 19 meV, delta2 ~ 6 meV, and fittings based on the Dynes model indicate that the dominant gap should have an anisotropic s-wave structure, this allow us to put the priority in selecting the s+- among the two arguable pairing models: s+- and d-wave in this thin films [6]. Our results indicate the undoubted role played by the spin fluctuations in establishing superconductivity in the two major nickelate superconducting systems. References: [1] Danfeng Li et al. Nature 527, 624(2019), [2] Hualei Sun et al. Nature 621, 493-498 (2023), [3] Qing Li et al. Commun. Mater. 1, 16 (2020, [4] Kejun Hu et al. Nat. Commun. 15, 5104 (2024), [5] Qiangqiang Gu et al. Nat. Commun. 11, 6027 (2020), [6] Shengtai Fan et al. arXiv. Condmat: arXiv:2506.01788.

Links

• Seminars at the IFW

Last modified: Jun 30, 2025, 7:39:43 AM