Merging of Single-Particle Levels and Non-Fermi-Liquid Behavior of Finite Fermi Systems

Abstract

We examine the problem of finite Fermi systems having a degenerate single-particle spectrum and show that the Landau approach, applied to such a system, admits the possibility of merging single-particle levels. It is demonstrated that the opportunity for this behavior is widespread in quantum many-body systems. The salient feature of the phenomenon is the occurrence of nonintegral quasiparticle occupation numbers, leading to a radical alteration of the standard quasiparticle picture. Implications of this alteration are considered for nuclear, atomic, and solid-state systems.

Doping-driven Mott transition inLa1−xSrxTiO3via simultaneous electron and hole dopin

“…21,22 Also, the insulating phase of the layered perovskite Ca 2 RuO 4 ͑4d 4 ͒ consists of a fully occupied t 2g band of predominant d xy character and two half-filled d xz,yz -like bands. 23,24 In view of the nearly complete orbital polarization of the Mott phase, it is evidently necessary to go beyond single-band models or multiband models for identical subbands to describe the effect of doping in these materials.…”

“…This approach is highly useful for the study of strong correlations in transition metal oxides. 24,27,29,30 Since it does not suffer from sign problems, the full Hund exchange including spin-flip and pair-exchange contributions can be taken into account. Also, relatively large Coulomb energies and low temperatures can be reached.…”

Entropy excess in strongly correlated Fermi systems near a quantum critical point

“…34,43 In finite Fermi systems, the phenomenon analogous to fermion condensation expresses itself as the merging of neighboring single-particle levels. 44 Interest in flat bands was ignited recently [45][46][47][48] in connection with a related opportunity to raise the critical temperature T c for termination of superconductivity of the electron systems in solids.…”

Flat bands and enigma of metamagnetic quantum critical regime in Sr3Ru2O7

“…(5) is the effective mass formed finally by some interaction, e.g. the Coulomb interaction, generating flat bands [39,46]. The characteristic wave number k max of the soft transverse zerosound mode is estimated as k max ∼ p F since we assume that the main contribution forming the flat band comes from vHs.…”