Bulk-sensitive Imaging of Twin Domains in La_{2-x}Sr_xCuO₄ under Uniaxial Pressure

We report our study of twin domains in $La_{2-x}Sr_x CuO_4$ under uniaxial pressure. Using bulk-sensitive x-ray microdiffraction in Laue geometry, we image the distribution of twin domains at room temperature. When compressive uniaxial pressure is applied along one of the in-plane crystallographic axes, the domain population changes dramatically. We observe that the twin domain with shorter lattice parameter along the direction of pressure is unstable under compression, and disappears completely with only moderate pressure. On the other hand, application of tensile pressure changes the domain structure only slightly, demonstrating the asymmetric response of the sample to uniaxial pressure. Our observations suggest that a crystal's response to uniaxial pressure is complex and could deviate easily from the linear-response regime.