Proximity-induced supercurrent through topological insulator based nanowires for quantum computation studies

Biplab Bhattacharyya,V P S Awana,V N Ojha,Sudhir Husale,T D Senguttuvan

doi:10.1038/s41598-018-35424-1

Abstract

Proximity-induced superconducting energy gap in the surface states of topological insulators has been predicted to host the much wanted Majorana fermions for fault-tolerant quantum computation. Recent theoretically proposed architectures for topological quantum computation via Majoranas are based on large networks of Kitaev’s one-dimensional quantum wires, which pose a huge experimental challenge in terms of scalability of the current single nanowire based devices. Here, we address this problem by realizing robust superconductivity in junctions of fabricated topological insulator (Bi2Se3) nanowires proximity-coupled to conventional s-wave superconducting (W) electrodes. Milling technique possesses great potential in fabrication of any desired shapes and structures at nanoscale level, and therefore can be effectively utilized to scale-up the existing single nanowire based design into nanowire based network architectures. We demonstrate the dominant role of ballistic topological surface states in propagating the long-range proximity induced superconducting order with high IcRN product in long Bi2Se3 junctions. Large upper critical magnetic fields exceeding the Chandrasekhar-Clogston limit suggests the existence of robust superconducting order with spin-triplet cooper pairing. An unconventional inverse dependence of IcRN product on the width of the nanowire junction was also observed.

Highlights

The increasing demand for faster and more powerful computational techniques has motivated researchers throughout the globe to shift attention towards quantum computation (QC) studies
The development of a ballistic Majorana nanowire device of InSb grown by Au-catalysed vapour-liquid-solid (VLS) mechanism[8] overrule the disorder related effects, but the practical Majorana-based future topological quantum computation (TQC) devices will mostly rely upon nanofabrication techniques like lithography and milling, where disorder will play a crucial role in hampering the topological phase of such semiconductor-based 1D Kitaev chains
Bprco[2] xviamluietsy-ecxocuepedleidngTtIhsewCithhapnodsrsaisbelkehsapri–nC-tlroipgsletot npaliimrinitgdoefmcoonospterratpeasitrhs.eTrhoebupsrtessuenpceercoofnldouncgt-irnagnpgeroppreorxtiimesiotyf effect with high IcRN product in the junctions suggests the dominant role of ballistic topological surface states (TSS) in propagating the supercurrent, even in the presence of diffusive bulk transport channels with barrier coherence length much smaller than the junction length of the devices

Summary

Introduction

The increasing demand for faster and more powerful computational techniques has motivated researchers throughout the globe to shift attention towards quantum computation (QC) studies. Majorana fermions (fermions that are their own anti-particles, i.e. unlike Dirac fermions, Majorana fermions have equal creation and annihilation operators,γ† = γ)[2,6] are predicted to occur as zero-energy excitations (Majorana zero modes, MZMs) in vortices of two-dimensional (2D) spinless p + ip superconductors; fractional quantum Hall effect (FQHE, ν = 5/2 state); and Kitaev’s model of 1D p-wave superconducting nanowire in topological phase[2,3]. These MZMs are expected to exhibit non-Abelian www.nature.com/scientificreports/. Most of these experiments were performed on TI-based nanowires, nanoribbons, nanoflakes, nanoplates or nanotubes, where the TSS conductance contribution is significantly enhanced due to large surface-to-volume ratio

Methods

Results

Discussion

Conclusion