The effect of strain on the SrTiO3/LaAlO3 heterointerface

Recent experiments have shown that it is possible to form a highly mobile, quasi-2D electron gas at the interface between SrTiO$_{3}$ and LaAlO$_{3}$. Although the origin of this effect is still debated, there is growing consensus that under certain growth conditions (e.g. high oxygen pressures) it is caused by the diverging electric potential within LaAlO$_{3}$ -the so-called polar catastrophe. One aspect of this system that has not been previously considered is the electric polarization of SrTiO$_{3}$, which can be effectively tuned by strain. This polarization can partially or fully compensate the diverging LaAlO$_{3}$ potential, and must be considered if SrTiO$_{3}$/LaAlO$_{3}$ is to be grown on a substrate such as Si. In this talk, an electrostatic model is presented to show how the polar catastrophe is modified by polarization within strained SrTiO$_{3}$. This model is supported by first-principles calculations on strained SrTiO$_{3}$/LaAlO$_{3}$ multilayers of varying thickness.