Showing papers on "Variable-range hopping published in 1968"
TL;DR: In this article, a discussion of conduction in glasses containing transition metal ions is presented, and the Miller-Abrahams term and polaron hopping term tend to zero, giving a decreasing slope of the ln p versus 1/T curve.
Abstract: In a discussion of conduction in glasses containing transition metal ions, the following points are stressed: 1. (a) The process is similar to “impurity conduction” in doped and compensated semi-conductors. 2. (b) There should be two terms in the activation energy, the Miller-Abrahams term and a polaron hopping term. 3. (c) Both terms should tend to zero, giving a decreasing slope of the ln p versus 1/T curve, as T → 0. 4. (d) The Heikes-Ure formula for the thermopower is discussed and a tentative explanation given of the difference between vanadium- and iron-containing glasses.
2,211 citations
TL;DR: In this paper, it is shown that no well-defined Fermi surface exists on the "metallic" side of the Mott transition in Hubbard's theory, and an alternative approach is suggested.
Abstract: It is shown that no well-defined Fermi surface exists on the "metallic" side of the Mott transition in Hubbard's theory. An alternative approach is suggested.
45 citations
TL;DR: In this paper, a self-consistent cluster treatment of Hubbard's Hamiltonian was used to study the magnetic effects in narrow bands, where electron hopping between lattice sites and Coulomb repulsion between electrons only on the same site was studied.
Abstract: Correlation and magnetic effects in narrow bands are studied using a new type of self‐consistent cluster treatment of Hubbard's Hamiltonian. Here the dynamics consist of electron hopping between lattice sites and Coulomb repulsion between electrons only on the same site. The environment of the cluster is regarded as a particle reservoir, one such for each spin. Hopping between the cluster and reservoirs is described by fermion source terms. It is required that the thermodynamic average of the particle currents of each spin within the cluster equal the corresponding particle exchange between cluster and reservoir. Electron motion in the system is examined for varying ratios of the strength of the hopping to the Coulomb repulsion. This is done as a function of electron density, spin, temperature, and external magnetic field. A Mott transition is found under dynamical conditions close to those predicted by Hubbard when there is one particle per site. For 〈n〉 ≠ 1, no metal insulator transition exists although...
23 citations