Effect of electron correlation on vibrational frequencies of Ag modes in C60

Noninvasive electrical detection of electron spin dynamics at the N atom in N@C60

Endohedral N@C(60) contains an electron spin of S = 3/2 at the central N atom, which, shielded by the C(60) cage, has an extremely long spin relaxation time. The π-conjugated C(60) cage, when connected to electrodes, provides a highly conductive path for electron transport and enables a noninvasive electrical detection of dynamics of the central spin. Here we use the Keldysh non-equilibrium Green's function and establish a microscopic description of how spin dynamics, including resonance and relaxation, can manifest itself in the device conductance. We predict that magnetic electrodes can enhance the detectivity by orders of magnitude compared with nonmagnetic electrodes. It is shown that this electrical detection is more sensitive to the longitudinal spin component than the transverse one. Hence the transient spin nutation is particularly useful in determining spin decoherence time T(2) in such transport device structures. This theory can be used to describe recent experiments of electrically detected spin dynamics in C(60) and other systems.

A complete nearest-neighbor force field model for C60

A force field model is developed for C(60) that features 13 force constants representing all interactions between nearest-neighboring atoms. The model is compared with, and tested against, other force field models in the literature. Force constants for C(60) are then deduced by fitting the model to the 14 known optically accessible vibrational frequencies of the molecule. Finally, the model is fitted to two existing theoretical calculations of the complete vibrational spectrum of C(60). Fair agreement is obtained with the theoretical calculations, implying that interactions with atoms other than nearest neighbors are small.