Properties of charge density waves in La$_{2-x}$Ba$_{x}$CuO$_4$

TL;DR

This study uses x-ray scattering to analyze charge density wave order in La$_{2-x}$Ba$_{x}$CuO$_4$ near x=1/8, revealing incommensurate, sinusoidal charge stripes with limited correlation length, and their relation to superconductivity suppression.

Contribution

First comprehensive x-ray scattering analysis of charge density waves in La$_{2-x}$Ba$_{x}$CuO$_4$ at x≈1/8, detailing incommensurate, sinusoidal charge order and its temperature evolution.

Findings

Charge density waves are incommensurate and sinusoidal.

Charge order develops around 40 K but remains short-range.

Correlation length saturates at ~230 Å and decreases below 15 K.

Abstract

We report a comprehensive x-ray scattering study of charge density wave (stripe) ordering in $\rm La_{2-x}Ba_xCuO_4 (x \approx 1/8)$, for which the superconducting $T_c$ is greatly suppressed. Strong superlattice reflections corresponding to static ordering of charge stripes were observed in this sample. The structural modulation at the lowest temperature was deduced based on the intensity of over 70 unique superlattice positions surveyed. We found that the charge order in this sample is described with one-dimensional charge density waves, which have incommensurate wave-vectors (0.23, 0, 0.5) and (0, 0.23, 0.5) respectively on neighboring $\rm CuO_2$ planes. The structural modulation due to the charge density wave order is simply sinusoidal, and no higher harmonics were observed. Just below the structural transition temperature, short-range charge density wave correlation appears, which develops into a large scale charge ordering around 40 K, close to the spin density wave ordering temperature. However, this charge ordering fails to grow into a true long range order, and its correlation length saturates at $\sim 230\AA$, and slightly decreases below about 15 K, which may be due to the onset of two-dimensional superconductivity.