Spectroscopic findings in SrTiO$_{3}$ applications: LaAlO$_{3}$/SrTiO$_{3}$ and La$_{0.7}$Sr$_{0.3}$MnO$_{3}$/SrTiO$_{3}$ heterostructures

Recently, a number of transport and magnetization studies have shown signs of exotic functionalities in SrTiO$_{3}$ based heterostructures, which are totally unexpected properties with no bulk analog in the constituent materials. However, it is still early stage to understand such a functionality, which limits improving SrTiO$_{3}$ applications. For this reason, we performed spectroscopic studies on the SrTiO$_{3}$ based heterostructures, such as LaAlO$_{3}$/SrTiO$_{3}$ and La$_{0.7}$Sr$_{0.3}$MnO$_{3}$/SrTiO$_{3}$ using element-specific techniques. For example, we found direct evidence for in-plane ferromagnetic order at the interface, with Ti$^{3+}$ character in the $d_{xy}$ orbital of the anisotropic $t_{2g}$ band in LaAlO$_{3}$/SrTiO$_{3}$ heterostructure. Also, we found that the unexpected metal to insulator transition in La$_{0.7}$Sr$_{0.3}$MnO$_{3}$/SrTiO$_{3}$ is due to changes in Mn 3$d$-electron confinement. These findings establish a striking example of emergent phenomena at oxide interfaces. In this presentation, I will introduce more details of spectroscopic findings on those heterostructures.