biostudies-literatureLiu WDeutsche Forschungsgemeinschaft (German Research Foundation)EC | EU Framework Programme for Research and Innovation H2020 | H2020 European Institute of Innovation and Technology (H2020 The European Institute of Innovation and Technology)3068https://www.ebi.ac.uk/biostudies/studies/S-EPMC11954865biostudies-literatureUnknown16(1)The fractional AC Josephson effect is a discerning property of topological superconductivity in hybrid Josephson junctions. Recent experimental observations of missing odd Shapiro steps and half Josephson frequency emission in various materials have sparked significant debate regarding their potential origin in the effect. In this study, we present microwave emission measurements on a resistively shunted Josephson junction based on a HgTe quantum well. We demonstrate that, with significant spurious inductance in the shunt wiring, the experiment operates in a nonlinear dynamic regime characterized by period-doubling. This leads to additional microwave emission peaks at half of the Josephson frequency, f_J/2, which can mimic the 4π-periodicity of topological Andreev states. The obsNature communicationsPeriod-doubling in the phase dynamics of a shunted HgTe quantum well Josephson junction.PMC11954865741734258499086390858490Kleinlein JBuhmann HLiang XMolenkamp LWFurst LStehno MPUpadhyay SPiatrusha SULiu WGould CfalsePeriod-doubling in the phase dynamics of a shunted HgTe quantum well Josephson junction.The fractional AC Josephson effect is a discerning property of topological superconductivity in hybrid Josephson junctions. Recent experimental observations of missing odd Shapiro steps and half Josephson frequency emission in various materials have sparked significant debate regarding their potential origin in the effect. In this study, we present microwave emission measurements on a resistively shunted Josephson junction based on a HgTe quantum well. We demonstrate that, with significant spurious inductance in the shunt wiring, the experiment operates in a nonlinear dynamic regime characterized by period-doubling. This leads to additional microwave emission peaks at half of the Josephson frequency, f_J/2, which can mimic the 4π-periodicity of topological Andreev states. The obs2025-01-01T00:00:00Z2025 Mar2025-07-02T03:04:52.509Z2025-07-02T03:04:52.509ZS-EPMC119548654015792510.1038/s41467-025-58299-z