Recent experimental and theoretical results for single-molecule transistors involving endohedral N@60 fullerene molecules are reported. The observed differential conductance shows a low-spin/high-spin transition of the molecules for increasing magnetic field, a feature never seen in devices fabricated with pure C60. We explain the observations in terms of the exchange interaction between electrons in the fullerene LUMO and the nitrogen p-electrons. The observations support an antiferromagnetic interaction. In addition, very soft vibrational modes are seen. We discuss a model Hamiltonian that reproduces the main features of the experimental conductance. The theoretical description employs the master-equation formalism in the sequential-tunneling approximation. Rapid dephasing is assumed, which allows to reduce the master equation to a set of rate equations. A number of open questions and possible solutions are pointed out.
Recent experimental and theoretical results for single-molecule transistors involving endohedral N@60 fullerene molecules are reported. The observed differential conductance shows a low-spin/high-spin transition of the molecules for increasing magnetic field, a feature never seen in devices fabricated with pure C60. We explain the observations in terms of the exchange interaction between electrons in the fullerene LUMO and the nitrogen p-electrons. The observations support an antiferromagnetic interaction. In addition, very soft vibrational modes are seen. We discuss a model Hamiltonian that reproduces the main features of the experimental conductance. The theoretical description employs the master-equation formalism in the sequential-tunneling approximation. Rapid dephasing is assumed, which allows to reduce the master equation to a set of rate equations. A number of open questions and possible solutions are pointed out.
