Doctor of Philosophy (PhD)
Physics and Astronomy
Nonlinear optical studies of bulk and thin film materials provide a vast playground for physical and dynamical characterization. In this thesis, we have implemented experimental methods to probe novel phase transitions in single crystals using rotational anisotropic second harmonic generation (RASHG) and carrier dynamics in thin films with time-resolved pump-probe reflectivity. Furthermore, a novel low temperature ultra-high vacuum system coupled to nonlinear optics has been developed to extend lab capabilities. Doping (Bi1-xSbx)2Se3 with antimony, the surface electronic reconstruction near x=80% was identified with RASHG by deviations in the six-fold and three-fold polarization anisotropic patterns. Development of RASHG techniques to include temperature control and vacuum conditions lead to the exploration of the temperature-dependent electronic phase transition of IrTe2. In IrTe2 the surface electronic transition at Tc~280 K measured by SHG is immediate and completes within the experimental temperature resolution. Comparing the surface temperate response to corresponding bulk measurements, the surface electronic transition occurs four times faster indicating the surface precedes the bulk transition. With time-resolved pump-probe reflectivity, an acoustic phonon mode in La0.67Sr0.33MnO3/SrTiO3 has been identified along with an anomalous low frequency oscillation unreported in similar systems.
Taylor, Joel E., "Nonlinear Optical Studies of Bulk and Thin Film Complex Materials" (2019). LSU Doctoral Dissertations. 4924.