Scaling behavior of heavy fermion metals

Abstract

a b s t r a c tStrongly correlated Fermi systems are fundamental systems in physics that are best studied experimentally, which until very recently have lacked theoretical explanations. This review discusses the construction of a theory and the analysis of phenomena occurring in strongly correlated Fermi systems such as heavy-fermion (HF) metals and two-dimensional (2D) Fermi systems. It is shown that the basic properties and the scaling behavior of HF metals can be described within the framework of a fermion condensation quantum phase transition (FCQPT) and an extended quasiparticle paradigm that allow us to explain the non-Fermi liquid behavior observed in strongly correlated Fermi systems. In contrast to the Landau paradigm stating that the quasiparticle effective mass is a constant, the effective mass of new quasiparticles strongly depends on temperature, magnetic field, pressure, and other parameters. Having analyzed the collected facts on strongly correlated Fermi systems with quite a different microscopic nature, we find these to exhibit the same non-Fermi liquid behavior at FCQPT. We show both analytically and using arguments based entirely on the experimental grounds that the data collected on very different strongly correlated Fermi systems have a universal scaling behavior, and materials with strongly correlated fermions can unexpectedly be uniform in their diversity. Our analysis of strongly correlated systems such as HF metals and 2D Fermi systems is in the context of salient experimental results. Our calculations of the non-Fermi liquid behavior, the scales and thermodynamic, relaxation and transport properties are in good agreement with experimental facts.

Scaling behavior of the thermopower of the archetypal heavy-fermion metal YbRh2Si2

“…1 (a), that depicts the behavior of the normalized specific heat (C/T ) N extracted from measurements of the specific heat C/T ∝ M * on YbRh 2 Si 2 under the application of magnetic fields B [5], where M * is the effective mass and T is temperature. It is seen that the curves (C/T ) N obtained in measurements at different magnetic fields B merge into a single one, exhibiting the scaling behavior [3,4,6]. This scaling behavior obtains an adequate description within the framework of fermion condensation theory (FC) that supports the extended quasiparticle paradigm [3,4].…”

“…It is seen that the curves (C/T ) N obtained in measurements at different magnetic fields B merge into a single one, exhibiting the scaling behavior [3,4,6]. This scaling behavior obtains an adequate description within the framework of fermion condensation theory (FC) that supports the extended quasiparticle paradigm [3,4].…”

“…Thus, we expect that within FC theory one can obtain an adequate description of the thermopower and its scaling behavior, for the theory is based on the quasiparticle paradigm [3,4,[14][15][16].…”

“…In such an event, quasiparticles of energy ε remain welldefined excitations near the chemical potential µ, ε ∼ µ [3,4], while the FC state itself is protected by topological invariants [17,18]. In the vicinity of FCQPT it is helpful to use "internal" scales to measure such quantities as e.g.…”

“…The NFL behavior is commonly characterized by a set of exponents of the temperature dependence of the physical properties, such as specific heat, resistivity, susceptibility etc. [1][2][3][4]. The LFL and NFL behaviors, and the crossover region cannot be captured by any single exponent as seen, for example, from Fig.…”