Tunable second harmonic in altermagnetic Josephson junctions

Abstract

We study electric- and Zeeman-field control of the Josephson effect in a planar superconductor–altermagnet–superconductor junction. The current-phase relation can be forward- or backward-skewed by a pronounced second harmonic whose strength depends on the altermagnetic field. Electric gating manipulates the skewness, while external fields can induce 0–π transitions and substantially enhance the critical current.