Gate-tunable Josephson diodes for cryogenic memory in magic-angle twisted bilayer graphene

Superconducting diodes (SDs) exhibit a non-reciprocal supercurrent response. Recently, SDs were reported in graphene-based moiré systems, which offer a promising platform to realize SDs based on Josephson junctions (JJs), since they host various tunable correlated phases [1, 2]. Here, we show gate-defined Josephson diode behavior in magic-angle twisted bilayer graphene, where we tune the weak link of the JJ to the correlated insulator at half-filling of the hole mini-band, reaching diode efficiencies up to 15%. We gain full control over the phase and polarity of the SDs by changing the carrier density of the weak link and the out-of-plane magnetic field. In an underdamped transport regime, we observe distinct hysteretic resistive switching when sweeping the current or magnetic field. This effect can be increased by coupling two gate-defined JJs in series, where we obtain stable hysteretic resistive switching even at zero magnetic field. This finding paves the way for integrating cryogenic memory cells into superconducting quantum devices.

[1] Díez-Mérida et al., Nat. Commun. 14, 2396 (2023)

[2] Lin et al., Nat. Phys. 18, 1221-1227 (2022)