Pei, Fei and Laird, E A and Steele, G. A. and Kouwenhoven, L. P. (2012) Valley-spin blockade and spin resonance in carbon nanotubes. Nature Nanotechnology, 7 (10). pp. 630-634. ISSN 1748-3395
Full text not available from this repository.Abstract
The manipulation and readout of spin qubits in quantum dots have been successfully achieved using Pauli blockade, which forbids transitions between spin–triplet and spin–singlet states1. Compared with spin qubits realized in III–V materials2,3,4,5, group IV materials such as silicon and carbon are attractive for this application because of their low decoherence rates (nuclei with zero spins)6,7. However, valley degeneracies in the electronic band structure of these materials combined with Coulomb interactions reduce the energy difference between the blocked and unblocked states8,9,10, significantly weakening the selection rules for Pauli blockade. Recent demonstrations of spin qubits in silicon devices have required strain and spatial confinement to lift the valley degeneracy7. In carbon nanotubes, Pauli blockade can be observed by lifting valley degeneracy through disorder11,12,13,14, but this makes the confinement potential difficult to control. To achieve Pauli blockade in low-disorder nanotubes, quantum dots have to be made ultrasmall8,9, which is incompatible with conventional fabrication methods. Here, we exploit the bandgap of low-disorder nanotubes to demonstrate robust Pauli blockade based on both valley and spin selection rules. We use a novel stamping technique to create a bent nanotube, in which single-electron spin resonance is detected using the blockade. Our results indicate the feasibility of valley–spin qubits in carbon nanotubes.