Mean Field study of the heavy fermion metamagnetic transition

TL;DR

This paper models the heavy fermion system's response to strong magnetic fields, revealing a metamagnetic transition characterized by a sudden polarization and susceptibility jump, aligning well with experimental data.

Contribution

It introduces an advanced hybridization mean field theory that captures the metamagnetic transition in heavy fermion compounds under magnetic fields.

Findings

Full polarization of spin-up quasiparticles at B*

Susceptibility becomes field-insensitive beyond B*

First-order transition to normal metallic state

Abstract

We investigate the evolution of the heavy fermion ground state under application of a strong external magnetic field. We present a richer version of the usual hybridization mean field theory that allows for hybridization in both the singlet and triplet channels and incorporates a self-consistent Weiss field. We show that for a magnetic field strength B*, a filling-dependent fraction of the zero-field hybridization gap, the spin up quasiparticle band becomes fully polarized--an event marked by a sudden jump in the magnetic susceptibility. The system exhibits a kind of quantum rigidity in which the susceptibility (and several other physical observables) are insensitive to further increases in field strength. This behavior ends abruptly with the collapse of the hybridization order parameter in a first-order transition to the normal metallic state. We argue that the feature at B* corresponds to the "metamagnetic transition" in YbRh2Si2. Our results are in good agreement with recent experimental measurements.