Gate-tunable supercurrent and multiple Andreev reflections in a superconductor-topological insulator nanoribbon-superconductor hybrid device

Abstract

We report on the observation of gate-tunable proximity-induced superconductivity and multiple Andreev reflections (MAR) in a bulk-insulating BiSbTeSe${}_2$ topological insulator nanoribbon (TINR) Josephson junction (JJ) with superconducting Nb contacts. We observe a gate-tunable critical current ($I_C$) for gate voltages ($V_g$) above the charge neutrality point ($V_{CNP}$), with $I_C$ as large as 430 nA. We also observe MAR peaks in the differential conductance ($dI/dV$) versus DC voltage ($V_{dc}$) across the junction corresponding to sub-harmonic peaks (at $V_{dc}=V_n=2{\Delta }_{Nb}/en$, where ${\Delta }_{Nb}$ is the superconducting gap of the Nb contacts and $n$ is the sub-harmonic order). The sub-harmonic order, $n$, exhibits a $V_g$-dependence and reaches $n=13$ for $V_g=40$ V, indicating the high transparency of the Nb contacts to TINR. Our observations pave the way toward exploring the possibilities of using TINR in topologically protected devices that may host exotic physics such as Majorana fermions.

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• Creating Majorana modes from segmented Fermi surface
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• Gate Tunable Supercurrent in Josephson Junctions Based on Bi2Te3 Topological Insulator Thin Films
• Influence of disorder on antidot vortex Majorana states in 3D topological insulators
• Gate-Tunable Ambipolar Josephson Current in a Topological Insulator
• Highly skewed current-phase relation in superconductor-topological insulator-superconductor Josephson junctions