Signatures of fractional Josephson effect in Josephson junctions based on the higher-order topological insulator WTe2
Yong Bin Choi (Postech, Pohang)
Jinho Park (Columbia University, Postech, Pohang)
Woochan Jung (Postech, Pohang)
Sein Park (Postech, Pohang)
Mazhar N. Ali (TU Delft - Applied Sciences, Kavli institute of nanoscience Delft)
Gil Ho Lee (Asia Pacific Center for Theoretical Physics, Pohang, Postech, Pohang)
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Abstract
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 [1–4] have identified conducting channels at the hinges of HOTIs, although their topological nature remains unexplored. In this study, we investigated Shapiro steps in Al‒WTe2‒Al proximity Josephson junctions (JJs) under microwave irradiation and examined the topological properties of the hinge states in WTe2. 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.
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