Pulsed electron spin resonance of an organic microcrystal by dispersive readout.

We establish a testbed system for the development of high-sensitivity Electron Spin Resonance (ESR) techniques for small samples at cryogenic temperatures. Our system consists of a NbN thin-film planar superconducting microresonator designed to have a concentrated mode volume to couple to a small amount of paramagnetic material, and to be resilient to magnetic fields of up to 400mT. At 65mK we measure high-cooperativity coupling (C≈19) to an organic radical microcrystal containing 1012 spins in a pico-litre volume. We detect the spin-lattice decoherence rate via the dispersive frequency shift of the resonator. Techniques such as these could be suitable for applications in quantum information as well as for pulsed ESR interrogation of very few spins to provide insights into the surface chemistry of, for example, the material defects in superconducting quantum processors.

Nanoelectromechanical switch operating by tunneling of an entire C60 molecule.

We present a solid state single molecule electronic device where switching between two states with different conductance happens predominantly by tunneling of an entire C60 molecule. This conclusion is based on a novel statistical analysis of approximately 10(5) switching events. The analysis yields (i) the relative contribution of tunneling, current induced heating and thermal fluctuations to the switching mechanism, (ii) the voltage dependent energy barrier (approximately 100-200 meV) separating the two states of the switch and (iii) the switching attempt frequency, omega0, corresponding to a 2.8 meV mode, which is most likely rotational.

Electron transfer dynamics of bistable single-molecule junctions.

We present transport measurements of single-molecule junctions bridged by a molecule with three benzene rings connected by two double bonds and with thiol end-groups that allow chemical binding to gold electrodes. The I-V curves show switching behavior between two distinct states. By statistical analysis of the switching events, we show that a 300 meV mode mediates the transition between the two states. We propose that breaking and reformation of a S-H bond in the contact zone between molecule and electrode explains the observed bistability.

Strong electronic coupling between single C60 molecules and gold electrodes prepared by quench condensation at 4 K. A single molecule three terminal device study.

We report the first measurements of single C60 molecules trapped in three terminal devices prepared by quench condensation of a gold source and drain electrode on top of an aluminium gate electrode covered with a thin oxide. Our experimental platform allows source and drain electrodes to be fabricated on the gate oxide at low temperatures and high vacuum. In a subsequent step, single molecules are evaporated in situ onto the surface and caught in the gap between a source and a drain electrode. This fabrication method ensures a clean contact between the molecule and the gold electrode due to the unbroken vacuum. Our measurements reveal a strong interaction between the C60 molecule and the gold electrodes resulting in the absence of the Coulomb blockade effects observed by others. In addition, we observe an insignificant gate dependence but a pronounced negative differential resistance (NDR) at bias voltages from 20-50 meV. The position of the peak in the NDR shows a pronounced and universal temperature dependence for all six devices included in the study. The results are related to previous measurements in such devices which focus on the detailed nature of the contact region between the molecule the gold electrode.