Energy scales and magnetoresistance at a quantum critical point

TL;DR

This paper investigates the magnetoresistance behavior near a quantum critical point in CeCoIn_5, revealing how effective mass scaling causes crossovers and energy scale separation between Fermi liquid and non-Fermi liquid regimes.

Contribution

It introduces a new understanding of MR and thermodynamic kink scaling behaviors at a QCP, linking them to quasiparticle effective mass and energy scale separation.

Findings

Identification of a crossover from negative to positive MR with temperature.

Discovery of kink features in thermodynamic properties at the QCP.

Revealing two distinct energy scales associated with LFL and NFL regimes.

Abstract

The magnetoresistance (MR) of CeCoIn_5 is notably different from that in many conventional metals. We show that a pronounced crossover from negative to positive MR at elevated temperatures and fixed magnetic fields is determined by the scaling behavior of quasiparticle effective mass. At a quantum critical point (QCP) this dependence generates kinks (crossover points from fast to slow growth) in thermodynamic characteristics (like specific heat, magnetization etc) at some temperatures when a strongly correlated electron system transits from the magnetic field induced Landau Fermi liquid (LFL) regime to the non-Fermi liquid (NFL) one taking place at rising temperatures. We show that the above kink-like peculiarity separates two distinct energy scales in QCP vicinity - low temperature LFL scale and high temperature one related to NFL regime. Our comprehensive theoretical analysis of experimental data permits to reveal for the first time new MR and kinks scaling behavior as well as to identify the physical reasons for above energy scales.