We investigate the strain response of underdoped HgBa2CuO4+δ (Hg1201), by synchrotron X-ray diffraction and corresponding simulations of thermal diffuse scattering. The compression in the crystallographic a direction leads to relatively small expansion in the b and c directions, with Poisson ratios νba=0.16 and νca=0.11, respectively. However, the Cu-O distance in the c direction exhibits a notable 0.9% increase at 1.1% a-axis compression. We further find strain-induced diffuse scattering which corresponds to a new type of two-dimensional charge correlation. Interestingly, this signal is insensitive to the onset of superconductivity and instead corresponds to a short-range, nearly commensurate modulation with a wave vector close to (0.5, 0, 0) and a correlation length of approximately four unit cells. It closely resembles the charge order theoretically predicted in the phase diagram of the spin-liquid model with resonating valence bonds on a square lattice.
@article{arxiv.2510.21343,
title = {Strain-induced structural change and nearly-commensurate diffuse scattering in the model high-temperature superconductor HgBa$_2$CuO$_{4+\delta}$},
author = {Mai Ye and Wenshan Hong and Tom Lacmann and Mehdi Frachet and Igor Vinograd and Gaston Garbarino and Sofia-Michaela Souliou and Michael Merz and Rolf Heid and Amir-Abbas Haghighirad and Yuan Li and Matthieu Le Tacon},
journal= {arXiv preprint arXiv:2510.21343},
year = {2026}
}