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

Understand

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.