Strain responses and transport properties in strontium titanate-based complex oxide devices

In this thesis, I summarize my work in mesoscale devices created in strontium titanate (SrTiO3)-based heterostructures, seeking to deepen the understanding of superconductivity and electron-pairing in those materials. Firstly, I summarize our observations of the long-lasting quasi-particle excitation using voltage or optical disturbances in SmTiO3/SrTiO3/SmTiO3 quantum wells in the pseudogap phase. Secondly, results demonstrating the effects of uniaxial stress on superconductivity in quantum wires at the LaAlO3/SrTiO3 interface created using conductive atomic force microscopy (c-AFM) are summarized. Superconductivity in the system is associated with ferroelastic domain boundaries at the conductive region edges and therefore is in the transition between 2D and 1D regimes. Both hysteretic and non-hysteretic responses to the strain in the system are closely examined. Under certain conditions, minute changes in uniaxial stress are found to abruptly and reversibly switch LaAlO3/SrTiO3 nanowires from a superconducting state to a normal state. Finally, the implications of these results are discussed in the context of the ferroelastic domain hypothesis.