Intercalation and High Temperature Superconductivity of Fullerides

Intercalation of polyatomic molecules into a superconductor can drastically affect the properties of the compound. A mechanism leading to a large increase in Tc for such systems is proposed. It explains the recent remarkable observation of high Tc superconductivity in the hole-doped C60/CHX3 (X=Cl,Br) compounds and the large shift in their Tc upon Cl->Br substitution. The increase in Tc is due to contribution to the pairing arising from the interaction of electrons with the vibrational manifold of the molecule. The proposed mechanism opens up the possibility to observe a site-selective isotope effect. We also suggest that intercalating CHI3 would further increase the critical temperature to Tc=140K.Comment: Final expanded version of cond-mat/0109553 and cond-mat/0110327 with Journal referenc

Dynamic coexistence of various configurations: clusters vs.nuclei

The presence of energy shells in metallic clusters and atomic nuclei leads to a peculiar relation between the number of particles N and the structure, and this leads to a strong correlation between the energy spectrum and N. An analysis of experimental data leads to the conclusion that, in addition to the static Jahn-Teller effect, the dynamic effect leading to the quantum coexistence of different configurations (quantum oscillations) plays an important role. Such suggested coexistence is an essential feature of clusters as well as nuclei, both finite Fermi systems.Comment: 6 pages, 2 figure

Correlation of normal and superconducting properties and unified approach to the description of high Tc oxides

We present a unified approach based on the Fermi liquid picture which allows us to describe the normal as well as the superconducting properties of the doped cuprates. The theory that is presented is for the doped compounds which are metallic. One can distinguish two interrelated, but nevertheless, different directions in the physics of high T(sub c): one involving the problem of carrier doping and the transition to the metallic state, and the second being the description of the metallic state. It is important that this metallic phase undergoes the transition into the superconducting state; as a result, our analysis is directly related to the origin of high T(sub c). We are using a quasi-2D Fermi liquid model to estimate the fundamental parameters of these very interesting materials. We find that this description is able to describe these materials and also that phonons and plasmons play a major role in the mechanism of high T(sub c)

Flat Thomas-Fermi artificial atoms

We consider two-dimensional (2D) "artificial atoms" confined by an axially symmetric potential $V(\rho)$. Such configurations arise in circular quantum dots and other systems effectively restricted to a 2D layer. Using the semiclassical method, we present the first fully self-consistent and analytic solution yielding equations describing the density distribution, energy, and other quantities for any form of $V(\rho)$ and an arbitrary number of confined particles. An essential and nontrivial aspect of the problem is that the 2D density of states must be properly combined with 3D electrostatics. The solution turns out to have a universal form, with scaling parameters $\rho^2/R^2$ and $R/a_B^*$ ($R$ is the dot radius and $a_B^*$ is the effective Bohr radius)