Topological Defects Coupling Smectic Modulations to Intra-unit-cell Nematicity in Cuprate

TL;DR

This study investigates the relationship between smectic modulations and intra-unit-cell nematicity in cuprate superconductors, revealing topological defects and proposing a Ginzburg-Landau model to explain their coupling and coexistence.

Contribution

It provides the first direct visualization of topological defects in smectic states and introduces a Ginzburg-Landau functional to describe their coupling with intra-unit-cell nematicity.

Findings

Identification of 2π topological defects in smectic states

Empirical evidence of coupling between defects and nematicity

A Ginzburg-Landau model explaining their coexistence

Abstract

We study the coexisting smectic modulations and intra-unit-cell nematicity in the pseudogap states of underdoped Bi2Sr2CaCu2O8+{\delta}. By visualizing their spatial components separately, we identified 2\pi topological defects throughout the phase-fluctuating smectic states. Imaging the locations of large numbers of these topological defects simultaneously with the fluctuations in the intra-unit-cell nematicity revealed strong empirical evidence for a coupling between them. From these observations, we propose a Ginzburg-Landau functional describing this coupling and demonstrate how it can explain the coexistence of the smectic and intra-unit-cell broken symmetries and also correctly predict their interplay at the atomic scale. This theoretical perspective can lead to unraveling the complexities of the phase diagram of cuprate high-critical-temperature superconductors.