Showing papers on "Mott transition published in 1968"

Absence of Mott Transition in an Exact Solution of the Short-Range, One-Band Model in One Dimension

Abstract: The short-range, one-band model for electron correlations in a narrow energy band is solved exactly in the one-dimensional case. The ground-state energy, wave function, and the chemical potentials are obtained, and it is found that the ground state exhibits no conductor-insulator transition as the correlation strength is increased.

The electronic and ionic structures of metal-ammonia solutions

Abstract: Presently existing data on the properties of liquid metal-ammonia solutions are reviewed critically in relation to physical models and current theory. Emphasis is given to the inter-relation between the electronic properties and the atomic structures of the solutions. The material is organized according to concentration regions characterized by differing electronic and ionic structures. In the very dilute concentration range, 0–10−3 mole per cent metal (MPM), the solutions behave as ideal electrolytes with solvated electrons and solvated positive ions as the ionic species. Association of these species occurs in the dilute region, 10−3–10−1 MPM. We propose that growth of associated complexes into large, metallic clusters occurs in the intermediate region, 10−1—3 MPM. A metal-non-metal transition or, at lower temperatures, a phase separation takes place in the 3–7 MPM concentration range. We give a simplified theory of the Mott transition for these solutions and explore the inter-relation of the Mo...

Comment on Hubbard's Theory of the Mott Transition

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.

Crystallization and magnetic ordering of an electron gas

Abstract: The possibility of crystallization and magnetic ordering in an electron gas is examined in the determinantal approximation, using a variational method. A Mott transition is found at rs similar, equals 10 to a ferromagnetic crystalline state of the Wigner type, while an antiferromagnetic crystalline phase seems to be excluded. A simple way of including correlation effects is proposed, in which a correlation function is introduced into the interaction energy between electrons of antiparallel spin. The possibility then emerges of a crystalline antiferromagnetic phase over the large intermediate density range 10 less, equals rs less, equals 40.

Correlation and Magnetic Effects in Narrow Energy Bands

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...

Comment on the discrepancy between the Jackson and Mott transition probability and the exact calculation of Secrest and Johnson.

Abstract: Transition probabilities for collinear collision of particle with harmonic oscillator, noting reasons for discrepancy in Jackson and Mott form

Model Calculations for the Study of Direct and Superexchange Interactions

Abstract: Investigations of the two‐atom M2+‐M2+ and the three‐atom M2+‐(F−)‐M2+ systems have been made in order to study both direct and superexchange mechanisms. In these model calculations all electrons are treated explicitly within the framework of the unrestricted Hartree‐Fock procedure; the Fock matrix is evaluated directly by Monte Carlo integration techniques. The effective exchange parameter J is determined at several internuclear distances, and spin densities are exhibited for the ferromagnetic and anti‐ferromagnetic states of the three‐atom system. The AF state lies lower in energy beyond a calculated critical bond length. Localization of the uhf eigenfunctions and the significance of the Mott transition for magnetic ordering are discussed.