Daily Overview: Today’s highlighted work focuses on deepening the understanding of the electronic structure of mixed Ruddlesden–Popper nickelates. In the paper provided today, the relevant study investigates bilayer nickelate films La2PrNi2O7 and La2SmNi2O7 grown on SrLaAlO4(001) substrates and explains the commonly observed incomplete zero resistance and two-step superconducting transition in their resistance measurements: azimuthal-angle-dependent measurements of circular-electrode devices show that the two-step feature is directly related to the substrate step–terrace orientation; when the current is parallel to the step edges, a single-step transition appears, whereas when it is perpendicular, the two-step transition is most pronounced, and ADF-STEM reveals structural disruption regions at the steps. On this basis, the authors model the film as intact regions with a higher transition temperature and step weak-link regions with a lower transition temperature, and use a simple model and finite-element simulations to reproduce the experimental features; the lateral size of the structural disruption regions, about 1–5 nm, is comparable to the Ginzburg–Landau in-plane coherence length of about 2–3 nm, supporting a Josephson-type weak-link picture. Transport measurements further show that the transition and even whether superconductivity appears depend strongly on the average terrace width: samples of about 920 and 540 nm can reach zero resistance, those of about 250 nm do not reach zero resistance, and those of about 120 nm lack superconductivity. This work identifies step-induced weak links as the microscopic origin of the two-step transition in bilayer nickelate films and provides a framework for understanding anisotropic and percolative transport and the low critical current. arXiv submission processing window: 2026-10-21 00:00 to 2026-10-21 00:00 UTC.
1. Superconducting weak links at substrate steps in bilayer nickelate films
- Relevance Score:
5.2388 - Authors: Yidi Liu, Yaoju Tarn, Lopa Bhatt, Puhua Zhang, Joonseo Song, Berit H. Goodge, David A. Muller, Harold Y. Hwang, Yijun Yu
- Affiliations: Stanford University, Max Planck Institute for Chemical Physics of Solids, Cornell University, SLAC National Accelerator Laboratory, Fudan University
- Link: https://arxiv.org/abs/2610.27729
- Paper page: Superconducting weak links at substrate steps in bilayer nickelate films
Summary: This study addresses bilayer nickelate films grown on SrLaAlO4(001) substrates (including La2PrNi2O7 and La2SmNi2O7) and explains the incomplete zero resistance and two-step superconducting transitions commonly observed in resistance measurements. Using circular-electrode devices, the azimuthal dependence of the transition was measured, revealing that the two-step feature is directly related to the substrate step–terrace orientation: when the current is parallel to the step edges, a single-step transition appears, whereas when it is perpendicular, the two-step transition is most pronounced; ADF-STEM also directly observed structural damage regions at the steps. On this basis, the films were modeled as intact regions with a higher transition temperature and step weak-link regions with a lower transition temperature, and simple models and finite-element simulations reproduced the experimental features; the lateral dimensions of the structural damage regions are approximately 1–5 nm, comparable to the Ginzburg-Landau in-plane coherence length of approximately 2–3 nm, supporting a Josephson-type weak-link picture. Transport measurements further show that the transition and even the occurrence of superconductivity depend strongly on the average terrace width: samples with average terrace widths of approximately 920 and 540 nm can reach zero resistance, those with approximately 250 nm do not reach zero resistance, and those with approximately 120 nm show no superconductivity. This work identifies step-induced weak links as the microscopic origin of the two-step transition in bilayer nickelate films and provides a framework for understanding anisotropic and percolative transport and low critical currents.