Strongly interacting fermion systems
Abstract
Research has been concentrated primarily in three areas: aspects of high temperature superconductor systems, electronic structure, and other strongly interacting systems. In high-temperature superconductors the three major developments were: (1) a mean-field treatment of the very popular t-J model that provided the first uniform exhibition of four different possible ground states, whose diversity poses serious challenges for more exact approaches; (2) a variational wavefunction was constructed for the t(sup i)-J model (a cousin of the t-J model) which has lower ground state energies than more exotic proposed grounds states with broken time-reversal symmetry, thus diluting the interest of the high-energy theorists in high-temperature superconductivity; and (3) the de Haas-van Alphen oscillations of the so-called marginal Fermi liquid have been computed for the first time. In the electronic structure program we note first, the work of John Mintmire, on polymer systems, especially chiral polymers such as polyethylene. Second, the most striking features of a calculation of the linear polarizability of rare-gas atoms are that good agreement for the frequency-dependent polarization is achieved by adjusting the gap between the occupied and unoccupied states to get the correct static polarizability, and that adding a few basis functions to the basis set already optimized for the total energy improves the convergence of the polarizability by three orders of magnitude. We review the understanding of the recently observed Shapiro steps in Josephson junction arrays which was achieved by uniting the dynamics of the two subsystems -- the flux lattice and the junction array -- to provide a global explanation which has a topological interpretation, thus suggesting wider applicability.
- Publication:
-
Unknown
- Pub Date:
- 1991
- Bibcode:
- 1991sifs.rept.....W
- Keywords:
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- Atomic Structure;
- Diamagnetism;
- Fermions;
- Josephson Junctions;
- Polarization (Charge Separation);
- Polyethylenes;
- Superconductivity;
- Electron Gas;
- Ground State;
- Neon;
- Oscillations;
- Rare Gases;
- Stereochemistry;
- Atomic and Molecular Physics