Fu Rou-Li

Layer Structure of Doped C60

It is found in this letter that the doped C60 possesses layer-structure in both bond distortions and electronic states. There are eight layers of carbon atoms in the charged C60, and its symmetry is reduced from Ih to D5d. This layer-structure indicates that there exist four nonequivalent groups of carbon atoms in the doped C60. It contrasts with the pristine C60, in which all the sixty carbon atoms are equivalent. One observable consequence of such layer-structure is the split of its NMR spectrum with the ratio 1:1:2:2.

Self-Trapping Process of Exciton in C60

A dynamical scheme is employed to simulate the self-trapping of the exciton in C60. During the self-trapping process, due to the bond distortion, two gap states A1u and A2u are separated from the highest occupied molecular orbital and the lowest unoccupied molecular orbital respectively. From the evolutions of the bond distortion and these two levels the relaxation time of the self-trapping exciton is about 90 fs. It is noticed that the relaxation of the exciton is much quicker than that of the charge transfer in C60.

Dynamical Process of Charge Transfer in Fullerene C60

We consider lattice relaxation in doped C60 using the tight-binding model applied to a single C60 molecule. To simulate the dynamical evolution processes of string polaron in charged C60, we use a classical dynamical method where all the tangential collective coordinates are chosen. The nonlinear response time of lattice relaxation can be obtained in view of the present theory.

Width of Soliton and the Electron Correlation in Polymer

The effect of electron correlation on the width of the soliton in polymer is studied. Our theory shows that the screening plays a key role in the effect of electron correlation on the width of soliton: In weak screening, the width of soliton is reduced by the electron-electron interaction; whereas, in strong screening, it will be increased. The physical reason is given at the end.

The screening effect of phonon modes in high-Tc oxide superconductor

This paper presents three different kinds of infrared (IR) spectra of oxide materials. The first one is the IR reflection spectra of Tl2Ba2Ca2Cu3O10 superconducting film at the incident angles 7°, 12° and 30°. The second one is the IR spectra of nonsuperconducting ceramic materials YBa2Cu3O6 and PrBa2Cu3O7. The third one is the IR spectra of superconductor YBa2Cu3O7-δ and of its film with the c-axis perpendicular to the film plane, as well as the changes in the spectra of these materials after annealing at different temperatures. It is found that in the spectra of high-Tc oxide superconductor, only the phonon modes along c-axis can be observed while the modes in a-b plane are absent. But in the spectra of nonsuperconductors the modes in a-b plane can be observed. Particularly in the absorption spectra of the semiconductor YBa2Cu3O6, all eleven allowed IR active modes have been detected. We suggest that the above experimental phenomena may result from the fact that the phonon modes vibrating in the a-b plane of the high-Tc oxide superconducting materials are almost screened by the free carriers which can move only in a-b plane.

Bond structure and electron states of charged C60

In the alkali-metal doped C60, the charge transfer induces the distortion of the bond structure and forms the self-trapping electronic bound states. Our theory manifests: 1, the charge transfer reduces the symmetry of C60 from Ih to D5d. 2, Both the bond distortion and the self-trapping states possess layer structures and are localized in the equatorial area. 3, The carbon atoms in charged C60 are divided into eight layers with an inversion center, then there exist four nonequivalent groups of carbon atoms. It makes the NMR line split into a fine structure with strength ratio 1: 1: 2: 2. 4, The charged C60 has two self-trapping bound states, one is 0.06 eV above HOMO with odd parity and the other is 0.05 eV below LUMO with even parity.