Universal Stripe Symmetry of Short-range Charge Density Waves in Cuprate Superconductors.

The omnipresence of charge density waves (CDWs) across almost all cuprate families underpins a common organizing principle. However, a longstanding debate of whether its spatial symmetry is stripe or checkerboard remains unresolved. While CDWs in lanthanum- and yttrium-based cuprates possess a stripe symmetry, distinguishing these two scenarios has been challenging for the short-range CDW in bismuth-based cuprates. Here, we  employed high-resolution resonant inelastic x-ray scattering to uncover the spatial symmetry of the CDW in Bi 2 $_2$ Sr 2 - x $_{2-x}$ La x $_{x}$ CuO 6 + δ $_{6+\delta }$ . Across a wide range of doping and temperature, anisotropic CDW peaks with elliptical shapes were  found in reciprocal space. Based on Fourier transform analysis of real-space models, we  interpret the results as evidence of unidirectional charge stripes, hosted by mutually 90 ∘ $^\circ$ -rotated anisotropic domains. Our  work paves the way for a unified symmetry and microscopic description of CDW order in cuprates. This article is protected by copyright. All rights reserved.