Broadband terahertz spectroscopy of the insulator-metal transition driven by coherent lattice deformation at theSmNiO3/LaAlO3interface

Abstract

We investigate the non-equilibrium insulator-metal transition driven in a SmNiO3 thin film by coherent optical excitation of the LaAlO3 substrate lattice. By probing the transient optical properties over a broad frequency range (100 -800 cm -1 ), we analyze both the time dependent metallic plasma and the infrared optical phonon line shapes. We show that the light-induced metallic phase in SmNiO3 has the same carrier density as the equilibrium metallic phase. We also report that the LaAlO3 substrate acts as a transducer only at the earlier time delays, as the vibrations are driven coherently. No long-lived structural rearrangement takes place in the substrate. Finally, we show that the transient insulator-metal transition occurs both below and above the Néel temperature. We conclude that the supersonic melting of magnetic order measured with ultrafast x-rays is not the driving force of the formation of the metallic phase. We posit that the insulator metal transition may origin from the rearrangement of ordered charges at the interface propagating into the film.

Multiple Supersonic Phase Fronts Launched at a Complex-Oxide Heterointerface

“…Ultrafast resonant soft x-ray diffraction experiments have, for example, revealed that a supersonic paramagnetic/antiferromagnetic front accompanies the insulator metal transition (IMT), propagating from the hetero-interface into the material [8]. Additional insight was provided by optical experiments in a related LaAlO 3 /SmNiO 3 heterostructure, in which the same substrate excitation was shown to induce an IMT in the nickelate film also above the Néel temperature [9]. This observation was taken as evidence that melting of magnetic order may follow the IMT and may not be its cause.…”

Dynamic Terahertz Plasmonics Enabled by Phase‐Change Materials

“…Many other materials showing dynamic THz responses applicable to active THz modulation also exist, such as NbO 2 , [211] InSb, [212,213] QWs, [214] titanium oxides, [215] orthoferrites, [216][217][218] rare-earth nickelates, [219][220][221] manganites, [222][223][224] topological insulators, [225][226][227] multiferroics, [228] molecular crystals, [229,230] medicines, [231] polymers, [232][233][234][235][236][237][238] and halide perovskites, [239][240][241][242][243][244][245][246] to name but a few. Considering the diversity of the material properties and the control mechanisms, plasmonic hybridization may bring about new possibilities for a wide variety of active THz devices.…”

Comparative study of nonequilibrium insulator-to-metal transitions in electron-phonon systems

“…2,3 Laser-induced mechanisms provide another strategy to manipulate quantum phases in these materials. [4][5][6][7] In these experiments, phase transitions or transitions to metastable states are induced by a time-dependent perturbation. The resulting dynamics often follows a highly nonthermal trajectory and in the context of IMTs interesting questions arise concerning both the timescale and the pathway for the non-adiabatic switching.…”