Investigation of heterostructuring as a tuning knob for NdNiO₃ phase transitions

Heterostructuring provides a tuning knob for correlated materials, allowing phase transitions to be driven apart and low dimensional phases to be stabilized. NdNiO₃ in its bulk state has concomitant para-antiferromagnetic and metal-insulator phase transitions. When two to four unit cell thick layers of NdNiO3₃ are interlaced with four unit cell thick NdAlO₃ layers, a highly confining interface is formed, hindering the charge disproportionation and breathing mode which is responsible for the bulk antiferromagnetic state. This separates T_N and T_MI in equilibrium and massively changes the timescales and energy requirements of driven ultrafast phase transitions. Here we investigate the dynamics of the metal-insulator transition in NdNiO₃/NdAlO₃ heterostructures using pump-probe reflectivity and resonant soft x-ray scattering measurements. These measurements show that even weak interfacial confinement has a very strong damping effect on a driven insulating to metallic transition, i.e., samples which otherwise have bulklike magnetic timescales have near identical dynamics to samples where the magnetic order has been frustrated by strong confinement. This result points to a requirement for a long-range structural transition for the metallic state to stabilize for long times in driven materials.