Picosecond evolution of an induced metallic state under infinitesimal optical doping in NdNiO3

Abstract

NdNiO3 is a rare-earth nickelate where competing interactions yield a thermally induced metal–insulator transition accompanied by simultaneous structural and magnetic transitions. In recent years, femtosecond time resolved measurements have emerged as powerful tools for studying nonequilibrium phases in such complex systems. In this work, we demonstrate that even at 110 K, well below the insulator–metal transition temperature, an infinitesimal ≈0.1% optical doping in nickel’s d-band can destabilize the insulating phase into a long-lived metallic phase that builds up in the first 5 ps after the pulsed excitation. Using the hysteresis free nature of the first-order transition in our sample, we infer the true lattice temperature from resistance measurement. The threshold temperature for the runaway metallization is identified with the start of the phase coexistence region. We thus conclude that simultaneous electron–hole injection is at least an order of magnitude more effective in suppressing the transition than doping by electrons or holes alone. The results also demonstrate that the homeostasis-like situations responsible for the stability in such complex systems are nevertheless susceptible to catastrophic failures under certain types of infinitesimal perturbations.