Optical Investigation of Dynamics and Couplings of Quasiparticles in Artificial Oxide Superlattices

Abstract

In condensed matters, the electronic, phononic, and magnetic properties are innately determined by its given crystal structure. The strength of dynamic coupling among these degrees of freedom is closely related to not only the noble physical phenomena, such as colossal magnetoresistance, superconductivity, and multiferroicity, but also the performance of electronic, phononic, and spintronic nanodevices. In this regard, the control of fundamental physical quantities is of critical importance, and an artificially designed superlattice (SL) structure can be one of candidates to control the physical quantities, having various geometrical parameters. In this thesis, I demonstrate the realization for the control of physical properties in a SL composed of ferromagnetic metal SrRuO3 and non-magnetic insulator SrTiO3. To investigate both the static and dynamic properties, I utilized the pump-probe techniques combined with several optical measurements. By manipulating the dimensionality of the layer within the SL and its periodicity, the thermal conductivity and the electron-phonon coupling in the SL can be precisely controlled. Furthermore, the angular momentum transfer process to thermalized chiral phonons is observed in real-time, and this proposes a new-platform to investigate chiral phonons using an artificial heterostructure.