Emergence of charge order in a staggered loop-current phase of cuprate high-temperature superconductors

TL;DR

This paper investigates how charge order and loop currents emerge and coexist in underdoped cuprate superconductors, revealing incommensurate modulations and symmetry-breaking phenomena linked to the pseudogap phase.

Contribution

It introduces a pi-loop current model that explains the emergence of charge order and incommensurate current patterns, highlighting the distinct roles of Coulomb interactions.

Findings

Loop currents emerge abruptly below van Hove filling.

Diagonal d-charge density waves are suppressed by loop currents.

Incommensurate current patterns break mirror and time-reversal symmetries.

Abstract

We study the emergence of charge ordered phases within a pi-loop current (piLC) model for the pseudogap based on a three-band model for underdoped cuprate superconductors. Loop currents and charge ordering are driven by distinct components of the short-range Coulomb interactions: loop currents result from the repulsion between nearest-neighbor copper and oxygen orbitals, while charge order results from repulsion between neighboring oxygen orbitals. We find that the leading piLC phase has an antiferromagnetic pattern similar to previously discovered staggered flux phases, and that it emerges abruptly at hole dopings p below the van Hove filling. Subsequent charge ordering tendencies in the piLC phase reveal that diagonal d-charge density waves (dCDW) are suppressed by the loop currents while axial order competes more weakly. In some cases we find a wide temperature range below the loop-current transition, over which the susceptibility towards an axial dCDW is large. In these cases, short-range axial charge order may be induced by doping-related disorder. A unique feature of the coexisting dCDW and piLC phases is the emergence of an incommensurate modulation of the loop currents. If the dCDW is biaxial (checkerboard) then the resulting incommensurate current pattern breaks all mirror and time-reversal symmetries, thereby allowing for a polar Kerr effect.