Research: Chiral heavy metal emerging from Kondo breakdown

In metals with local moments, the lattice Kondo effect generates a paramagnetic heavy Fermi liquid (FL). In situations with magnetic frustration, the breakdown of this Kondo effect can lead to topological non-Fermi liquids, most prominently the fractionalized Fermi liquid (FL*) where conduction electrons coexist with a spin-liquid background. We have identified a novel phase which can emerge near an FL-FL* quantum phase transition: If the FL* phase features a pi-flux U(1) spin liquid, then the onset of Kondo screening leads to a continuous change of the emergent gauge flux, resulting in a time-reversal-symmetry-breaking (i.e. chiral) metallic state. This chiral heavy-fermion metal is the two-band cousin
 of the staggered flux phase discussed for underdoped cuprate superconductors. We propose metallic pyrochlore magnets, such as Pr2Ir2O7, as candidate materials.

T. Drechsler, M. Vojta,
Emergent Chiral Metal near a Kondo Breakdown Quantum Phase Transition,
Phys. Rev. Lett. 134, 106503 (2025) (arXiv)