Deconfined criticality and ghost Fermi surfaces at the onset of antiferromagnetism in a metal

Abstract

We propose a general theoretical framework, using two layers of ancilla qubits, for a continuous transition between a Fermi liquid with a large Fermi surface, and a pseudogap metal with a small Fermi surface of electron-like quasiparticles. The pseudogap metal can be a magnetically ordered metal, or a fractionalized Fermi liquid (FL*) without magnetic order. A critical 'ghost' Fermi surface emerges (alongside the large electron Fermi surface) at the quantum critical point, with the ghost fermions carrying neither spin nor charge, but minimally coupled to (U (1) × U (1))/Z 2 or (SU (2) × U (1))/Z 2 gauge fields. Away from the critical point on the pseudogap side, the ghost Fermi surface absorbs part of the large electron Fermi surface, and leads to a jump in the Hall co-efficient. We also find an example of an "unnecessary quantum critical point" between a metal with spin density order, and a metal with local moment magnetic order. The ghost fermions contribute a T ln(1/T ) specific heat at temperature T at the critical point, and could also be detected in other thermal probes. We relate our results to the phases of correlated electron compounds.

Ultraviolet-Infrared Mixing in Marginal Fermi Liquids

“…To resolve these issues, it is crucial to understand the behaviors of the corresponding MFL theories. Moreover, understanding higher-order effects in nFLs in general may provide new insight on the nature of quantum phase transitions associated with sudden jumps of the FS size [26,27], and deconfined metallic quantum criticality [28][29][30][31].…”