Search

The ultrastrong coupling of single-electron tunneling and nanomechanical motion opens exciting opportunities to explore fundamental questions and develop new platforms for quantum technologies. We have measured and modeled this electromechanical coupling in a fully-suspended carbon nanotube device and report a ratio of $g_\mathrm{m}/\omega_\mathrm{m} = 2.72 \pm 0.14$, where $g_\mathrm{m}/2\pi = 0.80\pm 0.04$ GHz is the coupling strength and $\omega_\mathrm{m}/2\pi=294.5$ MHz is the mechanical resonance frequency. This is well within the ultrastrong coupling regime and the highest among all other electromechanical platforms. We show that, although this regime was present in similar fully-suspended carbon nanotube devices, it went unnoticed. Even higher ratios could be achieved with improvement on device design., Comment: 13 pages, 11 figures This new version contains the same model and analysis but applied to new experimental data compared to the previous version. This is why the coupling ratio is now 2.72 instead of 1.3 and most of the experimental parameters have changed

We examine environmental effects of surrounding nuclear spins on the electron spin relaxation of the N@C60 molecule (which consists of a nitrogen atom at the centre of a fullerene cage). Using dilute solutions of N@C60 in regular and deuterated toluene, we observe and model the effect of translational diffusion of nuclear spins of the solvent molecules on the N@C60 electron spin relaxation times. We also study spin relaxation in frozen solutions of N@C60 in CS2, to which small quantities of a glassing agent, S2Cl2 are added. At low temperatures, spin relaxation is caused by spectral diffusion of surrounding nuclear 35Cl and 37Cl spins in the S2Cl2, but nevertheless, at 20 K, T2 times as long as 0.23 ms are observed., Comment: 7 pages, 6 figures