The absence of odd Shapiro steps in microwave-irradiated Josephson junctions (JJs) is considered to be a possible indicator of 4π-periodic supercurrents that are induced by Majorana bound states. Here, by conducting measurements on Al/WTe2 JJs, the authors suggest that the missing first Shapiro step can instead arise from the intrinsic non-linearity of the current–voltage characteristics in low-to-moderate transparency junctions.
