Electron–Nuclear Interaction in \(^{13}C\) Nanotube Double Quantum Dots

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 enabling 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 \(^{13}C\) (nuclear spin \((I=\frac{1}{2})\) among the majority zero-nuclear-spin \(^{12}C\) atoms. We observe strong isotope effects in spin-blockaded transport, and from the magnetic field dependence estimate the hyperfine coupling in \(^{13}C\) nanotubes to be of the order of \(100 \mu eV\), two orders of magnitude larger than anticipated. \(^{13}C\)-enhanced nanotubes are an interesting system for spin-based quantum information processing and memory: the \(^{13}C\) nuclei differ from those 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.