sp3-Doped (6,5) Single-Walled Carbon Nanotubes as a New Class of Materials for Spin Qubit Technology

Single-walled carbon nanotubes (SWCNTs) doped with <i>sp3</i> defects are a promising class of optoelectronic materials with bright tunable photoluminescence and localized spin density. We study a series of <i>sp3</i> defects within (6,5) SWCNT that result in one single unpaired spin within the bandgap of the tube and show, using experimental and computational techniques, that this spin has a decoherence time competitive with molecular spin qubits. Density functional theory (DFT) studies indicate that an unpaired spin localizes around the defect site. We simulate dephasing of the localized spin by considering spin-nuclear spin bath interactions as the main source of decoherence at low temperature. We apply the cluster correlation expansion method with a pure-dephasing spin Hamiltonian to doped SWCNT in presence of solvent molecules at near 0 K and estimate the magnitude of the intrinsic dephasing time (T2). Combined with other decoherence mechanisms based on empirical parameters, we calculate a real dephasing time in good agreement with measured Hahn spin echo T2 and suggest a way to further improve dephasing time.<br/><br/>The authors acknowledge financial support from NSF DMR-19005990.