Our Work on Tunable Second Harmonics in Altermagnetic Josephson Junctions Published in Physical Review B
Our work on unconventional Josephson effects in altermagnetic Josephson junctions has been published in Physical Review B 111, 165406 (2025), in collaboration with the Prof. Songbo Zhang at Hefei National Laboratory and Dr. Chang-An Li and Prof. Bjoern Trauzettel at the University of Würzburg. The study reveals a pronounced influence of altermagnetism on the second harmonic of the Josephson current-phase relation and demonstrates effective control of the supercurrent and 0–π transitions by external electric and Zeeman fields.
Altermagnets combine zero net magnetization with momentum-dependent spin splitting, providing a distinct platform for exploring the interplay between unconventional magnetism and superconductivity. In this work, we systematically investigate phase-coherent transport in planar superconductor/altermagnet/superconductor Josephson junctions. We find that altermagnetism strongly modifies the second harmonic of the current-phase relation, giving rise to tunable forward- and backward-skewed Josephson responses and, in certain regimes, a dominant second-order Josephson effect.
We further show that electric gating can tune the skewness of the current-phase relation, drive 0–π transitions, and substantially enhance the critical supercurrent. An in-plane Zeeman field can likewise enhance the critical current and induce 0–π transitions. These results establish altermagnetic Josephson junctions as a highly tunable platform for higher-harmonic Josephson physics, with potential relevance to superconducting spintronics and controllable superconducting quantum devices.