Prof Arzhang Ardavan

Abstract:

Molecular nanostructures may constitute the fabric of future quantum technologies, if their degrees of freedom can be fully harnessed. Ideally one might use nuclear spins as low-decoherence qubits and optical excitations for fast controllable interactions. Here, we present a method for entangling two nuclear spins through their mutual coupling to a transient optically excited electron spin, and investigate its feasibility through density-functional theory and experiments on a test molecule. From our calculations we identify the specific molecular properties that permit high entangling power gates under simple optical and microwave pulses; synthesis of such molecules is possible with established techniques.

Abstract:

We present an electron paramagnetic resonance (EPR) study of ErSc2N@C80 fullerene in which there are two Er3+ sites corresponding to two different configurations of the ErSc2N cluster inside the C80 cage. For each configuration, the EPR spectrum is characterized by a strong anisotropy of the g factors (gx,y = 2.9, gz = 13.0 and gx,y = 5.3, gz = 10.9). Illumination within the cage absorption range (<600 nm) induces a rearrangement of the ErSc2N cluster inside the cage. We follow the temporal dependence of this rearrangement phenomenologically under various conditions.

Abstract:

The electron paramagnetic resonance (EPR) of spin-active metallofullerenes (MFs) La@ C82 and Sc@ C82 diluted in solid-state C60 crystalline matrices with molar concentrations varying from 0.4% to 100% are investigated. For dilute concentrations, the hyperfine structure of the MFs is resolved, and as the concentration increases exchange narrowing is observed leading to a single peak in the EPR. Sc@ C82 MFs are inserted into single-walled carbon nanotubes to form peapods with concentrations of 10% and 0.1%, diluted with C60. For the case of peapods containing 10% Sc@ C82 a strong narrow peak is observed in X -band CW EPR, but not pulsed measurements. Peapods containing Ce@ C82 MFs are prepared and these also show similar CW EPR to the Sc@ C82, indicating the peak arises from charge transfer with the SWNT. © 2010 The American Physical Society.

Abstract:

The ESR properties and crystal structures of solid-state La@C(82) in empty fullerene matrices were investigated by changing the concentration of La@C(82) and the species of an empty fullerene matrix: C(60), C(70), C(78)(C(2v)(3)), C(82)(C(2)) and C(84)(D(2d)(4)). The rotational correlation time of La@C(82) molecules tended to be shorter when La@C(82) is dispersed in larger fullerene matrices because large C(2n) molecules provide more space for La@C(82) molecules for rotating. La@C(82) dispersed in a hcp-C(82) matrix showed the narrowest hyperfine structure (hfs) due to the ordered nature of La@C(82) molecules in the C(82) crystal. On the other hand, in a C(60) matrix, La@C(82) molecules formed clusters because of the large different solubility, which leads to the ESR spectra being broad sloping features due to strong dipole-dipole and exchange interactions.