Fermion Condensation Quantum Phase Transition versus Conventional Quantum Phase Transitions

TL;DR

This paper compares fermion condensation quantum phase transition (FCQPT) with conventional quantum phase transitions (CQPT), highlighting how FCQPT leads to quasiparticle behavior with temperature-dependent effective mass, affecting universal properties in strongly correlated systems.

Contribution

It introduces the concept of FCQPT as a distinct quantum phase transition, emphasizing the role of quasiparticles with variable effective mass and explaining experimental observations in heavy-fermion metals.

Findings

Quasiparticles near FCQPT have temperature-dependent effective mass.

Universal behavior persists at higher temperatures in FCQPT compared to CQPT.

Experimental data on CeCoIn$_5$ support the FCQPT scenario.

Abstract

The main features of fermion condensation quantum phase transition (FCQPT), which are distinctive in several aspects from that of conventional quantum phase transition (CQPT), are considered. We show that in contrast to CQPT, whose physics in quantum critical region is dominated by thermal and quantum fluctuations and characterized by the absence of quasiparticles, the physics of a Fermi system near FCQPT or undergone FCQPT is controlled by the system of quasiparticles resembling the Landau quasiparticles. Contrary to the Landau quasiparticles, the effective mass of these quasiparticles strongly depends on the temperature, magnetic fields, density, etc. This system of quasiparticles having general properties determines the universal behavior of the Fermi system in question. As a result, the universal behavior persists up to relatively high temperatures comparatively to the case when such a behavior is determined by CQPT. We analyze striking recent measurements of specific heat, charge and heat transport used to study the nature of magnetic field-induced QCP in heavy-fermion metal CeCoIn$_5$ and show that the observed facts are in good agreement with our scenario based on FCQPT and certainly seem to rule out the critical fluctuations related with CQPT. Our general consideration suggests that FCQPT and the emergence of novel quasiparticles near and behind FCQPT and resembling the Landau quasiparticles are distinctive features intrinsic to strongly correlated substances.