Emergent surface superconductivity of nanosized Dirac puddles in a topological insulator

TL;DR

This paper reports the discovery of surface superconductivity in a topological insulator (Sb2Te3) at temperatures up to 60 K, arising in nanosized Dirac puddles, with potential implications for quantum computing.

Contribution

It demonstrates the emergence of high-temperature surface superconductivity in a topological insulator through chemical tuning, revealing a new state in Dirac puddles.

Findings

Superconductivity observed at ~9 K in Sb2Te3 with depleted bulk conduction.

Surface puddles exhibit superconductivity near 60 K and above.

Carrier mobility increased by two orders of magnitude after tuning.

Abstract

Surfaces of three-dimensional topological insulators have emerged as one of the most remarkable states of condensed quantum matter1-5 where exotic electronic phases of Dirac particles should arise1,6-8. Here we report a discovery of surface superconductivity in a topological material (Sb2Te3) with resistive transition at a temperature of ~9 K induced through a minor tuning of growth chemistry that depletes bulk conduction channels. The depletion shifts Fermi energy towards the Dirac point as witnessed by about two orders of magnitude reduction of carrier density and by very large (~25,000 cm^2/Vs) carrier mobility. Direct evidence from scanning tunneling spectroscopy and from magnetic response show that the superconducting condensate forms in surface puddles at unprecedentedly higher temperatures, near 60 K and above. The new superconducting state we observe to emerge in puddles can be tuned by the topological material's parameters such as Fermi velocity and mean free path through band engineering; it could potentially become a hunting ground for Majorana modes6 and lead to a disruptive paradigm change9 in how quantum information is processed.