Period-doubling in the phase dynamics of a shunted HgTe quantum well Josephson junction

Abstract

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 $4\pi$-periodicity of topological Andreev states. The observed current-voltage characteristics and emission spectra are well-described by a simple RCLSJ model. Furthermore, we show that the nonlinear dynamics of the junction can be controlled using gate voltage, magnetic field, and temperature, with our model accurately reproducing these effects without incorporating any topological attributes. Our observations urge caution in interpreting emission at $f_J/2$ as evidence for gapless Andreev bound states in topological junctions and suggest the appropriate parameter range for future experiments.

13 pages, 8 figures

References in corpus (8)

• Demonstration of an ac Josephson junction laser
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• AC Josephson effect in a gate-tunable Cd${}_3$As${}_2$ nanowire superconducting weak link

Cited by in corpus (6)

• Missing odd-order Shapiro steps do not uniquely indicate fractional Josephson effect
• Unveiling Topological Hinge States in the Higher-Order Topological Insulator WTe${}_2$ Based on the Fractional Josephson Effect
• Interedge backscattering in time-reversal symmetric quantum spin Hall Josephson junctions
• Limits of Thermal Conductance Quantization in Chiral Topological Josephson Junctions
• Self-Consistent Model for Gate Control of Narrow-, Broken-, and Inverted-Gap (Topological) Heterostructures
• AC Josephson Signatures of the Superconducting Higgs Mode