Edge dependent Josephson diode effect in WTe₂-based Josephson junction

The Josephson diode effect (JDE), a nonreciprocal supercurrent, is a cornerstone for future dissipationless electronics, yet achieving high efficiency in a simple device architecture remains a significant challenge. Here, we theoretically investigate the JDE in a junction based on monolayer 1T'-WTe_2. We first establish that different edge terminations of a WTe_2 nanoribbon lead to diverse electronic band structures, some of which host asymmetric edge states even with crystallographically equivalent terminations. This intrinsic asymmetry provides a natural platform for realizing the JDE. With a WTe_2-based Josephson junction, we demonstrate a significant JDE arising purely from these asymmetric edges when time-reversal symmetry is broken by a magnetic flux. While the efficiency of this edge-state-driven JDE is inherently limited, we discover a crucial mechanism for its enhancement: by tuning the chemical potential into the bulk bands, the interplay between edge and bulk transport channels boosts the maximum diode efficiency more than 50%. To interpret and rationalize these trends, we construct a minimal theoretical model for the Josephson potential that captures edge-bulk interference and quantitatively explains the numerical dependence on magnetic flux, chemical potential, and device geometry. Furthermore, we show that this enhanced JDE is robust against moderate edge disorder. Our findings not only propose a novel route to achieve a highly efficient JDE using intrinsic material properties but also highlight the potential of engineered WTe_2 systems for developing advanced superconducting quantum devices.