Broken SU(4) symmetry in a Kondo-correlated carbon nanotube

This paper reports on the experimental and theoretical investigation of nonequilibrium Kondo effect in carbon nanotube quantum dots. At low temperature and in the absence of magnetic field, the authors observe two symmetric satellite features on either side of the zero bias peak due to the splitting of single-particle states by the spin-orbit coupling and valley mixing. Further experimental results are discussed based on the underlying symmetries of the carbon nanotube energy spectrum.