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Quantum units from the topological engineering of molecular graphenoids

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Science  29 Nov 2019:
Vol. 366, Issue 6469, pp. 1107-1110
DOI: 10.1126/science.aay7203

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Controlling quantum defects in graphene

The development of quantum technologies relies on the ability to fabricate and engineer materials with robust quantum properties. The controlled introduction of defects in semiconductors is one of the most promising platforms under development. With the capability to precisely position point defects (five-membered rings) in the graphene honeycomb lattice, Lombardi et al. explored recent theoretical work suggesting that such defects should display enhanced quantum properties (see the Perspective by von Kugelgen and Freedman). The spin-bearing properties of the defects and the engineered control of their interactions open up exciting possibilities for graphene-based spintronics and quantum electronics.

Science, this issue p. 1107; see also p. 1070

Abstract

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. Here, we demonstrate that topological tailoring leads to superior quantum performance in molecular graphene nanostructures. We unravel the decoherence mechanisms, quantify nuclear and environmental effects, and observe spin-coherence times 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.

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