Carbon nanotubes for coherent spintronics

Carbon nanotubes (NTs) have been studied by material scientists since 19521, but became a worldwide research focus only after fullerenes were discovered and after single-walled carbon nanotubes (SWNTs) were introduced to the research community in 19932. The simplicity of their synthesis and the diversity of their properties3 quickly propelled NTs into electronics, optics, nanoand biotechnology research labs around the globe. Today’s nanofabrication techniques allow access to individual nanotubes, enabling novel integrated circuits4,5, fast6 or flexible7 transistors, nanomechanical oscillators8-10 and photoactive devices11-13. While the basic electronic properties of NTs have been the subject of previous reviews14,15, new quantum mechanical effects have been discovered recently. These are related to confinement of carriers in a quantum dot (i.e. a short NT segment displaying discrete energy levels), and to spin (i.e. intrinsic angular momentum and magnetic moment), and may shape the design of future quantum technologies. In this review we describe methods of fabrication of nanoscale quantum dot (QD) devices based on individual NTs, and discuss how they provide an understanding of electronic and nuclear spins and their interactions in NTs. These efforts are a step toward spintronic devices16 and solidstate quantum computation17 based on NTs. After reviewing the basics of NT synthesis and electronic properties we focus on three recent experiments: The fabrication of clean, suspended QDs and their role in revealing spin-orbit interactions18, the fabrication of top-gated, highly tunable double quantum dots (DQDs) and their response to nuclear spins19, and the potential of charge sensing and pulsed-gate techniques to study electronic spin dynamics20.