Conductivity Dynamics of the Metal to Insulator Transition in EuNiO3/LANiO3 Superlattices
Technical Report,15 Nov 2014,14 Aug 2015
University of California - San Diego La Jolla United States
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In numerous transition metal oxides TMO, competition between the charge, lattice, spin, and orbital degrees of freedom lead to emergent phenomena with the insulator-to-insulator transition IMT being one of the most enigmatic from fundamental and applied perspectives. Recently, considerable effort has focused on the growth of TMO heterostructures with atomic layer precision with a view towards controlling and even creating new emergent behavior including the IMT. Simultaneously, ultrafast optical spectroscopy UOS has become a powerful approach to interrogate emergence, probing how interactions and competition between operative degrees of freedom in TMOs determine macroscopic properties. In this STIR project an initial foray into non-equilibrium studies in nickelate superlattices was pursued to investigate IMT dynamics. Using time-resolved terahertz spectroscopy we measured the non-equilibrium recovery of the initial low temperature antiferromagnetic insulating phase following a picosecond quench to the high temperature paramagnetic metallic phase. Following photo-excitation, the recovery proceeds through nucleation and growth of the AFI phase at the expense of the PM phase following rapid cooling below the IMT transition temperature 150K. These results highlight the importance of mesoscopic physics in correlated materials revealing new length and timescales that arise during the course of a phase transition.