Current hot spot in the spin-valley blockade in carbon nanotubes

We present a theoretical study of the spin-valley blockade transport effect in a double quantum dot defined in a straight carbon nanotube. We find that intervalley scattering due to short-range impurities completely lifts the spin-valley blockade and induces a large leakage current in a certain confined range of the external magnetic field vector. This current hot spot emerges due to different effective magnetic fields acting on the spin-valley qubit states of the two quantum dots. Our predictions are compared to a recent measurement [F. Pei et al., Nat. Nanotech. 7, 630 (2012)]. We discuss the implications for blockade-based schemes for qubit initialization/readout, and motion sensing of nanotube-based mechanical resonators.