Spin-split masses and metamagnetic behavior of almost-localized fermions

Abstract

We discuss specific features of quasiparticles in a strong applied magnetic field and near the Mott-Hubbard localization: the strong spin dependence of the de Haasvan Alphen oscillations, the maximum in the field dependence of the linear specific-heat coefficient, and metamagnetic behavior. These properties are obtained within the approach involving auxiliary (slave boson) fields that provides both the Gutzwiller band narrowing and a nonlinear molecular field. The simultaneous observation of all three properties provides a consistent set of predictions of the mean-field approach to the almost-localized Fermi liquid. The situation for heavy fermion system CeRu2Siz is briefly discussed.Almost-localized systems of strongly correlated fermions comprise Mott-Hubbard systems [e.g., pure and doped Vz03 (Ref. 1) or La, , Sr"Ti03(Ref. 2)], heavy-fermion systems [such as UPt3, URu2Si2, or CeRu2Si2 (Ref. 3)], liquid He close to solidification, and high-temperature superconducting materials near the antiferromagnetic insulating state [e.g., La2 "Sr"CuO&for x-0.05 (Ref. 5) and YBa2Cu306+"for x-0.3 -0.4]. The first three classes of materials are frequently considered as Fermi liquids of almost localized quasiparticles, i.e. , the liquids bordering on a state with localized magnetic moments. The Fermi-liquid nature of their electronic or atomic (in the case of He) statesshould not be taken for granted, since close to the localization, regarded as a well-defined phase transition, one may encounter a soliton or other non-Fermi-liquid types of singleparticle excitations. The purpose of this paper is to propose a consistent set of experimentally verifiable predictions that determine the specific behavior of an almost-localized Fermi liquid in an applied magnetic field, treated within a simple single-particle approach. The lifetime effects for tempera-tures T~O, as well as the detailed applications to heavyfermion systems, will be discussed separately.In systems close to the Mott-Hubbard localization the band energy of quasiparticles is small (the effective mass m* -+~) and almost compensated by the short-range repulsive interaction among the carriers. In effect, the system is very susceptible to much weaker perturbations such as the exchange interactions (which lead to a spin-density wave formation on the itinerant side, and to antiferromagnetism on the insulating side), thermal noise (causing the disruption of a coherent band motion and a formation of localized moments at elevated temperature ), and applied magnetic field. The main goal of this paper is to show that the applied magnetic field induces a set experimentally verifiable new effects, namely, (i) a spectacular spin dependence of the effective mass as exhibited, e.g. , in de Haasvan Alphen oscillations, (ii) quasimetamagnetic behavior for the nonhalf-filled band case, and (iii) a strong and nonmonotonic magnetic field dependence of the linear specific-heat coefficient y. These effects should appear concurrently at low temperature.

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

“…In comparison to the results obtained within GA [9,38] we do not observe any spectacular metamagnetic transition for n < 1. The magnetization curves, especially in the intermediate interaction regime, are rather smooth and saturate gradually.…”

“…Indeed this kink can be singled out clearly on the field dependence of the magnetic susceptibility and the specific heat curves, as shown in Figs.4 and 5, respectively. One can say that the presence of both spin-dependent masses and the metamagnetic behavior signal an appearance of the so-called almost-localized Fermi liquid (ALFL) state, as such behavior is absent for the Landau Fermi liquid [38]. The diminution of .…”

Quasiparticle properties of strongly correlated electron systems with itinerant metamagnetic behavior

“…Metamagnetic behavior is shown to also occur in situations where the Fermi energy lies close to a van Hove singularity [4,5], or where a Pomeranchuk Fermi surface deformation instability occurs [6]. It has been shown by calculations based on the Gutzwiller approximation by Vollhardt [7] and Spalek and coworkers [8][9][10] that for a generic concave density of states metamagnetic behavior is also found in the intermediate coupling regime of the Hubbard model. The metamagnetic scenario is then that of correlated electrons, with a (Mott) localization tendency due to the interaction.…”

“…The European Physical Journal B to describe itinerant metamagnetism for correlated electrons [2][3][4][5][9][10][11][12] due to its relative formal simplicity. We employ the dynamical mean field theory (DMFT) [11,13] combined with the numerical renormalization group (NRG) [14,15] to solve the effective impurity problem.…”

Cooper Pair with Nonzero Momentum in System with Spin Dependent Mass of Quasiparticles

“…Namely, electrons in the spin--majority (σ = ↑) band have the quasiparticle mass m 1 ≡ m ↑ different than the electrons with their spin in the opposite direction, m 2 ≡ m ↓ [2,3]. This situation takes place for instance in the CeCoIn 5 superconductor [4].…”