Signatures of fractional Josephson effect in Josephson junctions based on the higher-order topological insulator WTe2

Higher-order topological insulators (HOTIs) represent a novel class of topological materials, characterised by the emergence of topological boundary modes at dimensions two or more lower than those of bulk materials. Recent experimental studies 1 , 2 , 3 , 4 have identified conducting channels at the hinges of HOTIs, although their topological nature remains unexplored. In this study, we investigated Shapiro steps in Al‒WTe 2 ‒Al proximity Josephson junctions (JJs) under microwave irradiation and examined the topological properties of the hinge states in WTe 2 . Specifically, we analysed the microwave frequency dependence of the absence of the first Shapiro step in hinge-dominated JJs, which is consistent with a contribution from a 4π-periodic current‒phase relationship characteristic of topological JJs. These findings encourage further research into topological superconductivity in superconducting hybrid devices based on HOTIs. • Al/WTe2/Al Josephson junctions were fabricated to compare bulk- and hinge-dominated transport in HOTI-candidate WTe2. • Two junction types yield different bulk-to-hinge transport ratios. • Missing first Shapiro step is observed only in hinge-dominant junctions. • RCSJ modeling suggests a 4π-periodic CPR contribution in hinge-dominant JJs.