Emergent loop current order from pair density wave superconductivity

TL;DR

This paper demonstrates that pair density wave states in cuprates can induce a novel loop current order that explains various experimental observations like magnetic order and Kerr effect, highlighting a new link between superconductivity and symmetry breaking.

Contribution

It reveals that PDW states can generate a time-reversal and parity breaking loop current order, providing a unified explanation for multiple experimental phenomena in cuprates.

Findings

Loop current order arises from PDW states.

The secondary order breaks time-reversal and parity symmetries.

The phase explains magnetic order, Kerr effect, and charge density wave observations.

Abstract

There is evidence that the pseudogap phase in the cuprates breaks time-reversal symmetry. Here we show that pair density wave (PDW) states give rise to a translational invariant nonsuperconducting order parameter that breaks time-reversal and parity symmetries, but preserves their product. This secondary order parameter has a different origin, but shares the same symmetry properties as a magnetoelectric loop current order that has been proposed earlier in the context of the cuprates to explain the appearance of intracell magnetic order. We further show that, due to fluctuations, this secondary loop current order, which breaks only discrete symmetries, can preempt PDW order, which breaks both continuous and discrete symmetries. In such a phase, the emergent loop current order coexists with spatial short-range superconducting order and possibly short-range charge density wave (CDW) order. Finally, we propose a PDW phase that accounts for intracell magnetic order and the Kerr effect, has CDW order consistent with x-ray scattering and nuclear magnetic resonance observations, and quasi-particle properties consistent with angle-resolved photoemission scattering.