Fig. 2: Electron spin resonance of endofullerenes.
From: Readout and control of an endofullerene electronic spin
a Single-spin electron paramagnetic resonance (EPR) realized using double electron–electron resonance (DEER) in the double-quantum (DQ) basis. Brown pulses (dotted lines) and red pulses (continuous lines) address 0 → +1 and 0 → −1 nitrogen vacancy (NV) transitions, respectively. b Low-temperature DEER-DQ spectroscopy on a single NV center in diamond. The solid brown and purple lines indicate the simulated spectrum of a single N@C60, and weakly coupled spin-bath (g = 2.03), respectively (linewidths reduced to 1 MHz for clarity). The solid blue line indicates the combined simulation with experimental linewidth. The simulated endofullerene has an isotropic hyperfine constant a = 19 MHz, axial zero-field splitting D = 1.52 MHz and a static magnetic field B0 = 9.697 mT (see Supplementary Section 2). Dotted vertical lines indicate positions of ensemble EPR hyperfine components. Error bars depict photon shot noise. c Spectrum decays under room-temperature (RT) thermo-optical load, solid line indicates fit to single Lorentzian model. Dotted lines indicate positions of ensemble EPR hyperfine components. Error bars depict photon shot noise. d Ensemble solution EPR data on the same N@C60 sample measured across ∼109 spins. e Pulse sequence comparing NV center Hahn-echo decoherence in presence (first RF sequence) and absence (second RF sequence) of an RF spin-flip on N@C60. f Direct comparison of the temporal evolution of the NV Hahn-echo signal with and without a spin-flip on the coupled N@C60. g Difference in NV center decoherence at short evolution times versus longer evolution times reveals the clear separation of timescales at which the NV–N@C60 interaction is dominant.
