The field-free and highly efficient diodes with the nonreciprocity of supercurrent are believed to be the core block of the superconducting computing devices without dissipation. In this paper, we propose a Josephson diode based upon altermagnets with the vanishing net macroscopic magnetization. The nonreciprocity of supercurrent can be realized without applying any external magnetic field or ferromagnetic exchange field, which can avoid the magnetic cross-talk between the basic elements of the devices. The high efficiency exceeding $40\%$ can be obtained and the efficiency shows the high stability when the structure parameters are changed. The diode efficiency is antisymmetric about the relative orientation angle of the superconducting leads, so that its sign can easily be inverted by adjusting the relative orientation angle. The symmetries satisfied by the current-phase difference relations and the diode efficiency are analyzed by considering the transformations of the junctions under the time-reversal, the spin-rotation and the mirror reflection operations. The high efficiency and the high stability of the Josephson diode effect in our junctions provide the possibility for the design of the field-free dissipationless diode devices.
Spin-Polarized Josephson Supercurrent in Nodeless Altermagnets
Zhejiang University（浙江大学）；Hefei National Laboratory（合肥国家实验室）；University of Science and Technology of China（中国科学技术大学）；University of Chinese Academy of Sciences（中国科学院大学）
Josephson effects in the spin-triplet superconductor/altermagnet/spin-triplet superconductor junctions: the detection of the intrinsic $\bf{d}$-vector
School of Science, Qingdao University of Technology（青岛理工大学理学院）；International Center for Quantum Materials, School of Physics, Peking University（北京大学物理学院量子材料科学中心）；Hefei National Laboratory（合肥国家实验室）
Altermagnetic superconducting diode effect from non-collinear compensated magnetism in Mn$_3$Pt
Hearne Institute of Theoretical Physics, Department of Physics & Astronomy, Louisiana State University（路易斯安那州立大学）；Department of Physics, Indian Institute of Technology Delhi（印度理工学院德里分校）；Institute for Theoretical Physics III, University of Stuttgart（斯图加特大学）
Phase Transitions in Disordered Altermagnetic Josephson Junctions
Hefei National Laboratory（合肥国家实验室）；School of Emerging Technology, University of Science and Technology of China（中国科学技术大学先进技术研究院）；Institute for Theoretical Physics and Astrophysics, University of Würzburg（维尔茨堡大学理论物理与天体物理研究所）
Pair Density Waves and Supercurrent Diode Effect in Altermagnets
The University of Tennessee（田纳西大学）；Oak Ridge National Laboratory（橡树岭国家实验室）；Hanyang University（汉阳大学）；Technische Universität München（慕尼黑工业大学）；Munich Center for Quantum Science and Technology (MCQST)（慕尼黑量子科学与技术中心）；Imperial College London（帝国理工学院）
Gate-Switchable Josephson Diode Effect in Graphene via Magnetochiral Anisotropy
School of Optoelectronic Information Engineering, Shangrao Normal University（上饶师范学院光电信息工程学院）；School of Mathematics and Physics, Shangrao Normal University（上饶师范学院数学与物理学院）
Supercurrent spin Hall effect enabled nanopillar Josephson diodes
School of Physical Sciences, National Institute of Science Education and Research (NISER)（国家科学教育研究中心物理科学学院）；Homi Bhabha National Institute（霍米·巴巴国立研究所）；Center for Interdisciplinary Sciences, National Institute of Science Education and Research (NISER)（国家科学教育研究中心交叉科学中心）
Field-free Josephson diode and tunable $ϕ_0$-junction in chiral kagome antiferromagnets
Hefei National Laboratory（合肥国家实验室）；Center for Correlated Matter and School of Physics, Zhejiang University（浙江大学关联物质中心与物理学院）；School of Emerging Technology, University of Science and Technology of China（中国科学技术大学新兴技术学院）
Néel-Vector Control of the Josephson Diode Effect in $\mathcal{PT}$-symmetric Antiferromagnets
Anhui Province 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低能量子材料与器件安徽省重点实验室）；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）
Controllable Josephson diode effect, $0$-$π$ transition and switch effect in the superconductor/two-dimensional Weyl nodal line semimetal/superconductor junctions
Josephson diode and spin-valve effects on the surface of altermagnet CrSb
Institute of Solid State Physics of the Russian Academy of Sciences（俄罗斯科学院固体物理研究所）；V.L. Ginzburg Research Centre for High-Temperature Superconductivity and Quantum Materials, P.N. Lebedev Physical Institute of RAS（俄罗斯科学院列别杰夫物理研究所V.L.金兹堡高温超导与量子材料研究中心）
Phase-Controlled Majorana Zero Modes in Altermagnetic Topological-Insulator Josephson Junctions
Huazhong University of Science and Technology（华中科技大学）；Tsung-Dao Lee Institute（李政道研究所）；School of Physics and Astronomy, Shanghai Jiao Tong University（上海交通大学物理与天文学院）；High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences（中国科学院合肥物质科学研究院高磁场实验室）；College of Physics and Optoelectronic Engineering, Department of Physics, Jinan University（暨南大学物理与光电工程学院）；Hefei National Laboratory（合肥国家实验室）；Shanghai Research Center for Quantum Sciences（上海量子科学研究中心）
