Quantum phase transition from an antiferromagnet to a spin liquid in a metal

TL;DR

This paper investigates quantum phase transitions in Kondo-Heisenberg systems, revealing that fractionalized Fermi liquids exhibit universal critical behavior unaffected by weak Kondo coupling, contrasting with traditional theories.

Contribution

It demonstrates that in fractionalized Fermi liquids, the critical properties are robust against weak Kondo coupling, challenging conventional Hertz-Millis theory predictions.

Findings

Critical properties are unaffected by weak Kondo coupling in fractionalized Fermi liquids.

Electron quasiparticles remain well-defined at the quantum critical point.

Critical spin fluctuations contribute only subleading corrections to conduction electron properties.

Abstract

We study quantum phase transitions from easy-plane antiferromagnetic metals to paramagnetic metals in Kondo-Heisenberg lattice systems. If the paramagnetic metal is a fractionalized Fermi liquid then the universal critical properties of the phase transition are unaffected for a weak Kondo coupling even when the Fermi surface intersects the magnetic zone boundary. This is in striking contrast to the conventional theory of phase transitions between paramagnetic and antiferromagnetic metals where any Kondo coupling is strongly relevant, and leads to a Landau-damped `Hertz-Millis' theory. The electron quasi-particle remains well-defined in the quantum critical regime and the critical spin fluctuations only contribute subleading corrections to the various properties of conduction electrons.