Emerging quantum critical phase in a cluster spin-glass

TL;DR

This study uncovers a quantum critical phase in a disordered cluster spin-glass system, revealing quantum criticality and Fermi surface changes associated with Kondo breakdown in a heavy-fermion metal.

Contribution

It demonstrates the emergence of quantum criticality and Fermi surface expansion in a cluster spin-glass driven by intrinsic disorder, expanding understanding of non-symmetry-breaking quantum phases.

Findings

Quantum critical scaling observed near 0.13 Tesla.

Suppression of the spin-glass phase with increasing magnetic field.

Evidence of Fermi surface expansion post-critical point.

Abstract

Magnetic frustration has been recognized as pivotal to investigating new phases of matter in correlation-driven Kondo breakdown quantum phase transitions that are not clearly associated with broken symmetry. The nature of these new phases, however, remains underexplored. Here, we report quantum criticalities emerging from a cluster spin-glass in the heavy-fermion metal TiFe$_x$Cu$_{2x-1}$Sb, where frustration originates from intrinsic disorder. Specific heat and magnetic Gr\"uneisen parameter measurements under varying magnetic fields exhibit quantum critical scaling, indicating a quantum critical point near 0.13 Tesla. As the magnetic field increases, the cluster spin-glass phase is progressively suppressed. Upon crossing the quantum critical point, resistivity and Hall effect measurements reveal enhanced screening of local moments and an expanding Fermi surface, consistent with the Kondo breakdown scenario.