Relevance of indirect tunneling in twisted cuprate Josephson diode junctions

Investigate whether indirect quasiparticle tunneling via localized states contributes to negative Josephson coupling and time-reversal-symmetry breaking in twisted Bi2Sr2CaCu2O8+x Josephson junctions that exhibit a field-free Josephson diode effect, and assess if such processes account for the large second-harmonic Josephson term required in existing phenomenological models.

Background

Negative Josephson coupling has been invoked to explain the Josephson diode effect in twisted high-Tc cuprate two-dimensional crystals, often attributed to d-wave pairing. However, the magnitude of the required second-order term in the Josephson energy suggests additional mechanisms may be at play.

Given the demonstrated role of indirect tunneling via localized states in producing negative coupling in the present ALD-fabricated junctions, the authors highlight that its potential relevance in twisted cuprate junctions has not yet been investigated.