Controlling symmetry of spin-orbit entangled pseudospin state through uniaxial strain

In layer-structured $\mathrm{S}{\mathrm{r}}₂\mathrm{Ir}{\mathrm{O}}₄$, strong crystal electric field and spin-orbit coupling result in an intriguing spin-orbit entangled ${J}_{\mathrm{eff}}=1/2$ state, resembling the spin $S=1/2$ state of high-temperature superconducting cuprates. Our study unravels the intricate relationship between the lattice and the pseudospin interactions using uniaxial strain. Applied along the [1 1 0] direction, a compressive strain does not induce any effect. In contrast, the strain along [1 0 0] triggers a dramatic detwinning of the magnetic domains bringing the system to a single domain at around 0.04% strain. The strain driven detwinning rate is temperature independent showing that it does not exhibit a spontaneous orthorhombic lattice distortion driven by the pseudo-Jahn-Teller effect.