Hole dynamics in an antiferromagnet across a deconfined quantum critical point

TL;DR

This paper investigates how a small density of holes affects a square lattice antiferromagnet near a deconfined quantum critical point, proposing a non-Fermi liquid phase with fractionalized excitations and analyzing electronic spectra relevant to cuprate experiments.

Contribution

It introduces the concept of a holon metal phase emerging at the critical point with fractionalized excitations and analyzes the electronic spectrum using boundary critical theory.

Findings

Identification of a non-Fermi liquid 'holon metal' phase.

Discontinuous change in Fermi surface area ratio across the critical point.

Electronic spectra resemble 'Fermi arc' features observed in cuprates.

Abstract

We study the effects of a small density of holes, delta, on a square lattice antiferromagnet undergoing a continuous transition from a Neel state to a valence bond solid at a deconfined quantum critical point. We argue that at non-zero delta, it is likely that the critical point broadens into a non-Fermi liquid `holon metal' phase with fractionalized excitations. The holon metal phase is flanked on both sides by Fermi liquid states with Fermi surfaces enclosing the usual Luttinger area. However the electronic quasiparticles carry distinct quantum numbers in the two Fermi liquid phases, and consequently the limit of the ratio A_F/delta, as delta tends to zero (where A_F is the area of a hole pocket) has a factor of 2 discontinuity across the quantum critical point of the insulator. We demonstrate that the electronic spectrum at this transition is described by the `boundary' critical theory of an impurity coupled to a 2+1 dimensional conformal field theory. We compute the finite temperature quantum-critical electronic spectra and show that they resemble "Fermi arc" spectra seen in recent photoemission experiments on the pseudogap phase of the cuprates.