Electron-nuclear interaction in 13C nanotube double quantum dots

TL;DR

This study investigates hyperfine interactions in 13C nanotube double quantum dots, revealing strong isotope effects and hyperfine coupling, which are promising for spin-based quantum information processing.

Contribution

It provides the first experimental measurement of hyperfine coupling in 13C nanotubes with variable nuclear concentration, highlighting their potential for quantum memory applications.

Findings

Strong isotope effects observed in spin-blockaded transport.

Estimated hyperfine coupling around 100 micro-eV, larger than theoretical predictions.

Enhanced 13C concentration significantly affects spin dynamics.

Abstract

For coherent electron spins, hyperfine coupling to nuclei in the host material can either be a dominant source of unwanted spin decoherence or, if controlled effectively, a resource allowing storage and retrieval of quantum information. To investigate the effect of a controllable nuclear environment on the evolution of confined electron spins, we have fabricated and measured gate-defined double quantum dots with integrated charge sensors made from single-walled carbon nanotubes with a variable concentration of 13C (nuclear spin I=1/2) among the majority zero-nuclear-spin 12C atoms. Spin-sensitive transport in double-dot devices grown using methane with the natural abundance (~ 1%) of 13C is compared with similar devices grown using an enhanced (~99%) concentration of 13C. We observe strong isotope effects in spin-blockaded transport, and from the dependence on external magnetic field, estimate the hyperfine coupling in 13C nanotubes to be on the order of 100 micro-eV, two orders of magnitude larger than anticipated theoretically. 13C-enhanced nanotubes are an interesting new system for spin-based quantum information processing and memory, with nuclei that are strongly coupled to gate-controlled electrons, differ from nuclei in the substrate, are naturally confined to one dimension, lack quadrupolar coupling, and have a readily controllable concentration from less than one to 10^5 per electron.