Evidences for d-wave symmetry of c-axis superconducting gap in atomically thin twisted flakes of bismuth-based HTS cuprates

• Published in: Physica. C, Superconductivity Vol. 623; p. 1354549
• Main Author: Talantsev, Evgeny F.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.08.2024
• Subjects: Ambegaokar-Baratoff model; Critical currents; Pairing symmetry; Twisted cuprate junctions; Twisted cuprate junctions; Pairing symmetry; Ambegaokar-Baratoff model; Critical currents
• ISSN: 0921-4534; 1873-2143
• DOI: 10.1016/j.physc.2024.1354549

c-axis Josephson tunnelling in atomically thin twisted flakes of quasi-two-dimensional cuprate superconductors is one of the experimental techniques which can be used to reveal the pairing symmetry in HTS cuprates. Until very recent experiments reported by Zhao et al. (Science382, 1422 (2023)), there was a widely accepted consensus that the c-axis Josephson currents, Ic(T), in twisted cuprate junctions manifest the s-wave gap symmetry for c-axis gap component. Here, I highlighted that this consensus was based on the analysis of the Ic(T) data by using the Ambegaokar-Baratoff equation, where the weak-coupling s-wave gap equation was utilized. In this study, I introduced a more accurate gap equation in the AB model and reanalyzed the Ic(T) data in atomically thin twisted Bi2Sr2-xLaxCuO6+y (Bi-2201) and Bi2Sr2CaCu2O8+x (Bi-2212) flakes. In the result, the analysis revealed evidences for d-wave pairing symmetry. Beside this, the analysis of the RnIc(T) data reported by Zhao et al. (Science382, 1422 (2023)) by a piecewise AB model, where a linear low-T dependence of the Ic(T) is used, and where the threshold temperature TM is a free-fitting parameter, confirmed the d-wave symmetry in these twisted Bi-2212 junctions.