Thermal‐Driven Diode Polarity Switching From Competing Helical Superconducting States in WTe ₂ /α‐Fe ₂ O ₃ Heterostructures

Abstract

ABSTRACT The superconducting diode effect has recently received considerable attention in condensed matter physics as a sensitive probe of symmetry‐broken and unconventional superconducting states. Here, we explore the superconducting diode effect in lateral Nb‐proximitized Josephson junctions composed of WTe 2 and antiferromagnetic insulating α‐Fe 2 O 3 , a heterostructure that exhibits both pronounced Rashba spin‐orbit coupling and a small net magnetization. We observe a robust and nonvolatile Josephson diode response, where the diode polarity can be initialized through pre‐training with both in‐plane and out‐of‐plane magnetic fields. Moreover, we uncover a thermal‐driven polarity switching, in which the diode polarity is reversed by heating above the superconducting transition and cooling back into the superconducting state, indicating a deterministic transition between competing superconducting states. Our theoretical calculations substantiate that these behaviors can be attributed to the formation of distinct helical superconducting states associated with opposite‐directed center‐of‐mass momenta. These findings establish the Josephson diode effect as a powerful probe of competing superconducting states in systems with broken inversion and time‐reversal symmetries, providing insight into the interplay between spin–orbit coupling, magnetism, and unconventional superconductivity.