Jozef Spałek

Simple treatment of the metal-insulator transition: Effects of degeneracy, temperature, and applied magnetic field

A simple slave-boson representation combined with the Hartree-Fock approximation for Hunds rule coupling is introduced for a doubly degenerate narrow band, which bears a direct relation to that introduced previously in the nondegenerate case. Namely, one keeps the fermion representation of the spin operator to recover properly the energy of fermionic quasiparticles in the presence of an applied magnetic field. A simple two-parameter mean-field analysis of the metamagnetism is provided, with the emphasis on the role of Hunds rule coupling. We also analyze the appearance of the spin-split effective masses in the applied field and for the non-half-filled band situation. The Mott-Hubbard boundary is determined at nonzero temperature

Renormalized mean-fieldt−Jmodel of high-Tcsuperconductivity: Comparison to experiment

(Tg0)

Consistent statistical treatment of the renormalized mean-field t − J model

; it shifts towards lower interactions with increasing

Even-parity spin-triplet pairing by purely repulsive interactions for orbitally degenerate correlated fermions

T

Coexistence of spin-triplet superconductivity with magnetism within a single mechanism for orbitally degenerate correlated electrons: statistically consistent Gutzwiller approximation

and the field signaling the precursory localization effects, explicitly exhibited in the behavior of the magnetic susceptibility calculated in the Appendix. We also formulate a more general two-parameter rotationally invariant approach for an arbitrary degeneracy

Ferromagnetism in UGe2: A microscopic model

d

High-temperature superconductivity in the two-dimensional t-J model: Gutzwiller wavefunction solution

of equivalent orbitals and show that the Mott-Hubbard transition at zero temperature and at any integer filling

Anderson lattice with explicit Kondo coupling revisited: metamagnetism and the field-induced suppression of the heavy fermion state.

ng~1

Spin-triplet superconducting pairing due to local Hund’s rule and Dirac exchange

is always discontinuous. A brief overview of the experimental situation is also given.

Properties of an almost localized Fermi liquid in an applied magnetic field revisited: a statistically consistent Gutzwiller approach

Using an advanced version of the renormalized mean-field theory (RMFT) for the t-J model, we examine spin-singlet superconducting (SC) state of