2024/03/02 by Jinxin Hu, Hu, Jin-Xin, Shuai A. Chen +3 · 1 citation
Physics and Astronomy · #FOS: Physical sciences #Physics of Superconductivity and Magnetism #Superconductivity (cond-mat.supr-con)
paper · pdf · doi:10.48550/arxiv.2403.01080
openalex publication_date 2024/03/02 · openalex created_date 2024/03/06 · openalex updated_date 2026/07/28
Nonreciprocal critical supercurrents give rise to the superconducting diode effect (SDE) in noncentrosymmetric superconductors when time-reversal symmetry is broken. In this paper, we investigate the SDE in superconductors with vanishing spin-orbit coupling but featuring narrow bands near the Fermi energy -- a characteristic particularly relevant to moiré heterostructures, such as twisted bilayer graphene. Using phenomenological Ginzburg-Landau theory and self-consistent mean-field approaches, we analyze the contributions to the SDE from both conventional band dispersion and quantum geometry. While the conventional SDE arises from the asymmetric Fermi surface, we demonstrate that the quantum metric dipole generates a band quantum-geometric contribution to the SDE, even in systems with symmetric single-particle dispersion. Notably, in the flat-band limit, where the attractive interaction strength significantly exceeds the bandwidth, the contributions from quantum geometry to the supercurrent and diode effect become dominant. Our paper elucidates the conventional and quantum-geometric origins of superconducting nonreciprocity and explores their implications for flat-band superconductors.