Quantum transport in carbon nanotubes covalently functionalized with magnetic molecules

Abstract

We report on quantum transport measurements of a carbon nanotube (CNT) quantum dot that is functionalized with magnetic {Mn-4} complexes. The coupling between the spin-5/2 Mn-II ions within each {Mn-4} complex is predominantly antiferromagnetic. Coulomb diamond measurements at T=4K reveal that the covalent attachment of the complexes to the CNT framework has only little influence on the carbon nanotube quantum dot. Surprisingly, a strong increase of noise is observed upon cooling the sample to T=30 mK. Time traces of the current taken at a diamond edge reveal a random telegraph signal. We attribute this to fluctuations of molecular spin states of the attached {Mn-4} complexes.