Nematic single-component superconductivity and loop-current order from pair-density wave instability

TL;DR

This paper explores how pair-density wave instabilities can lead to nematic and loop-current orders in superconductors, providing insights into anisotropic fluctuations and vestigial phases relevant to cuprate superconductors.

Contribution

It introduces a model linking PDW instabilities to nematic and loop-current vestigial phases, highlighting their emergence and properties in superconducting materials.

Findings

Identification of vestigial nematic and loop-current phases from PDW instability

Prediction of highly anisotropic superconductor stiffness in underdoped cuprates

Correlation of theoretical results with experimental observations of anisotropic fluctuations

Abstract

We investigate the nematic and loop-current type orders that may arise as vestigial precursor phases in a model with an underlying pair-density wave (PDW) instability. We discuss how such a vestigial phase gives rise to a highly anisotropic stiffness for a coexisting single-component superconductor with low intrinsic stiffness, as is the case for the underdoped cuprate superconductors. Next, focusing on a regime with a mean-field PDW ground state with loop-current and nematic $xy$ (B$_{2g}$) order, we find a preemptive transition into a low and high-temperature vestigial phase with loop-current and nematic order corresponding to $xy$ (B$_{2g}$) and $x^2-y^2$ (B$_{1g}$) symmetry respectively. Near the transition between the two phases, a state of soft nematic order emerges for which we expect that the nematic director is readily pinned away from the high-symmetry directions in the presence of an external field. Results are discussed in relation to findings in the cuprates, especially to the recently inferred highly anisotropic superconducting fluctuations [W{\aa}rdh {\em et al.}, ``Colossal transverse magnetoresistance due to nematic superconducting phase fluctuations in a copper oxide'', arXiv:2203.06769], giving additional evidence for an underlying ubiquitous PDW instability in these materials.