Detection of Spin Reversal via Kondo Correlation in Hybrid Carbon Nanotube Quantum Dots

We experimentally investigate the electronic transport through a double-wall carbon nanotube filled with Fe nanoparticles. At very low temperatures, the Kondo effect is observed between the confined electrons in the nanotube quantum dot and the delocalized electrons in the leads connecting the nanotube. We demonstrate that the presence of magnetic nanoparticles in the inner core of the nanotube results in a hysteretic behavior of the differential resistance of the system when the magnetic field is varied. This behavior is observed in the Kondo diamonds of the stability diagram, and the magnitude of hysteresis varies with the strength of the Kondo correlations in different diamonds. Our findings are corroborated with accurate numerical renormalization group calculations performed for an effective low-energy model involving fluctuations of the spin on the orbital level of the nanotube due to spin flips of the nanoparticles.