Thermal-Driven Diode Polarity Switching From Competing Helical Superconducting States in WTe₂/α-Fe₂O₃ Heterostructures.

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 WTe₂ and antiferromagnetic insulating α-Fe₂O₃, 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.