Quantum units from the topological engineering of molecular graphenoids

Controlling quantum defects in graphene

Robustly coherent spin centers that can be integrated into devices are a key ingredient of quantum technologies. Vacancies in semiconductors are excellent candidates, and theory predicts that defects in conjugated carbon materials should also display long coherence times. However, the quantum performance of carbon nanostructures has remained stunted by an inability to alter the sp² -carbon lattice with atomic precision.

The scientists from Oxford University/TU Dresden/MPIP have demonstrated that topological tailoring leads to superior quantum performance in molecular graphene nanostructures, which opens completely new perspectives for graphene spintronics. The saddle-shaped polycyclic hydrocarbon, synthesized by the team of Prof. Xinliang Feng in TU Dresden, possesses an open-shell singlet biradical structure in the ground state and exhibits high stability under ambient conditions (t_1/2=39 days). The group led by Prof. Lapo Bogani in Oxford University used the pulsed electron paramagnetic resonance to investigate the quantum properties of this interesting biradicaloid. The decoherence mechanisms, quantify nuclear and environmental effects were clearly unraveled, and large spin-coherence times (T_m) were observed that outclass most nanomaterials. These results validate long-standing assumptions on the coherent behavior of topological defects in graphene and open up the possibility of introducing controlled quantum-coherent centers in the upcoming generation of carbon-based optoelectronic, electronic, and bioactive systems. This fruitful results of the joint research have been now published in the renowned journal “Science”.

This research is a joint collaboration between scientists from the Oxford University, Technische Universität Dresden and the Max Planck Institute for Polymer Research (MPIP). The authors gratefully acknowledge financial support by the European Union (ERC-StG-338258- OptoQMol, ERC-CoG-773048-MMGNRs, ERC-CoG-819698-T2DCP, Graphene Flagship-Core2-696656, and European Social Fund); the Royal Society (University Research Fellow and URF grant); UKEPSRC EP/L011972/1; German DFG (Excellence Cluster CFAED and EnhanceNano-391979941); and the Max Planck Gesellschaft and Saxony ESF-Project-GRAPHD.

Reference: 
Federico Lombardi, Alessandro Lodi, Ji Ma, Junzhi Liu, Michael Slota, Akimitsu Narita, William K. Myers, Klaus Müllen, Xinliang Feng, Lapo Bogani. Quantum units from the topological engineering of molecular graphenoids. Science 2019, 366 (6469), 1107-1110.