In contrast to bulk materials with complex electronic structure, artificial nanoscale devices could offer a new and simpler vista to the understanding of quantum phase transitions. This paper demonstrates this possibility in a single molecule quantum dot, where the quantum phase transition consists of a crossing of singlet and triplet electron spin states at zero magnetic field. The quantum dot is operated in the Kondo regime, where an uncompensated electron spin on the quantum dot is screened by metallic electrodes. This strong electronic coupling between the quantum dot and the metallic contacts provides the necessary strong electron correlations to observe quantum critical behaviour.
- Nicolas Roch
- Serge Florens
- Franck Balestro
