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.
Quantum superconducting diode effect with perfect efficiency above liquid-nitrogen temperature
Beijing Academy of Quantum Information Sciences（北京量子信息科学研究院）；Tsinghua University（清华大学）；Southern University of Science and Technology（南方科技大学）；Hefei National Laboratory（合肥国家实验室）；Institute of Physics, Chinese Academy of Sciences（中国科学院物理研究所）；Brookhaven National Laboratory（布鲁克海文国家实验室）；Frontier Science Center for Quantum Information（量子信息前沿科学中心）；RIKEN Center for Emergent Matter Science (CEMS)（理化学研究所新兴物质科学中心）
2.4 GHz Flip-flop Device within Nonequilibrium Superconducting Diode
National Laboratory of Solid State Microstructures and Collaborative Innovation Center of Advanced Microstructures, Nanjing University（南京大学固态微结构国家重点实验室与先进微结构协同创新中心）；College of Engineering and Applied Sciences, Nanjing University（南京大学工程与应用科学院）；School of Materials Science and Engineering, Zhangjiang Institute for Advanced Study, Shanghai Jiao Tong University（上海交通大学张江高等研究院材料科学与工程学院）；School of Physics, Nanjing University（南京大学物理学院）；State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Science（中国科学院上海硅酸盐研究所高性能陶瓷与超微结构国家重点实验室）
Programmable superconducting diode from nematic domain control in FeSe
Max Planck Institute for Structure and Dynamics of Matter（马克斯·普朗克物质与结构动态研究所）；University of Bristol（布里斯托大学）；Los Alamos National Laboratory（洛斯阿拉莫斯国家实验室）；Wills Physics, University of Bristol（布里斯托大学威尔斯物理系）；HFML-FELIX（高磁场实验室-费利克斯）
Field-Free Superconducting Diode Enabled by Geometric Asymmetry and Perpendicular Magnetization
Beihang University（北京航空航天大学）；Beijing Superstring Academy of Memory Technology（北京超弦存储技术研究院）；Toyota Riken-Kyoto University Research Center (TRiKUC)（丰田理研京都大学研究中心）；Qingdao Research Institute, Beihang University（北京航空航天大学青岛研究院）
Algebraic Criterion and Graph-Theoretic Construction of Intrinsic Superconducting Diode Effects
Anhui Provincial Key Laboratory of Low-Energy Quantum Materials and Devices, High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences（中国科学院合肥物质科学研究院强磁场科学中心安徽省低能量子材料与器件重点实验室）；Science Island Branch of Graduate School, University of Science and Technology of China（中国科学技术大学研究生院科学岛分院）
Large superconducting diode effect driven by edge states in twisted iron-chalcogenide Josephson junctions
Tsung-Dao Lee Institute, Shanghai Jiao Tong University（上海交大李政道研究所）；College of Information Science and Electronic Engineering, Zhejiang University（浙江大学信息与电子工程学院）；School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院）；Department of Physics, City University of Hong Kong（香港城市大学物理系）；Zhangjiang Institute for Advanced Study, Shanghai Jiao Tong University（上海交通大学张江高等研究院）；Hefei National Laboratory（合肥国家实验室）；New Cornerstone Science Laboratory（新基石科学实验室）
Vortex structure and intervortex interaction in superconducting structures with intrinsic diode effect
Moscow Institute of Physics and Technology（莫斯科物理技术学院）；Institute for Physics of Microstructures, Russian Academy of Sciences（俄罗斯科学院微观物理研究所）；ITMO University（ITMO大学）；University of Iceland（冰岛大学）；University of Bordeaux（波尔多大学）；Sechenov First Moscow State Medical University（谢切诺夫第一莫斯科国立医科大学）
Diode effect in Shapiro steps in an asymmetric SQUID with a superconducting nanobridge
Moscow Institute of Physics and Technology（莫斯科物理技术学院）；Institute for Physics of Microstructures, Russian Academy of Sciences（俄罗斯科学院微观物理研究所）；Laboratory for Condensed Matter Physics, HSE University（高等经济大学凝聚态物理实验室）；National University of Science and Technology MISIS（国立科技大学MISIS）；Dukhov Research Institute of Automatics (VNIIA)（杜霍夫自动装置科学研究所以）
Vortex-driven superconducting diode effect in asymmetric multilayer heterostructures
Institute for Advanced Study in Physics, Zhejiang University（浙江大学物理高等研究院）；Zhejiang Key Laboratory of Micro-Nano Quantum Chips and Quantum Control, School of Physics, Zhejiang University（浙江大学物理学院微纳量子芯片与量子控制浙江省重点实验室）；International Quantum Academy, Shenzhen（深圳国际量子研究院）；Collaborative Innovation Center of Advanced Microstructures, Nanjing University（南京大学先进微结构协同创新中心）
