By combined top- and backgating, we explore the correlation of superconductivity with band filling and electron confinement at the LaAlO3-SrTiO3 interface. We find that the top- and backgate voltages have distinctly different effects on the superconducting critical temperature, implying that the confining potential well has a profound effect on superconductivity. We investigate the origin of this behavior by comparing the gate-dependence of Tc to the corresponding evolution of the band filling with gate voltage. For several backgate voltages, we observe maximum Tc to consistently coincide with a kink in tuning the band filling for high topgate voltage. Self-consistent Schr\"odinger-Poisson calculations relate this kink to a Lifshitz transition of the second dxy subband. These results establish a major role for confinement-induced subbands in the phase diagram of SrTiO3 surface states, and establish gating as a means to control the relative energy of these states.
@article{arxiv.1801.02881,
title = {Correlation between Superconductivity, Band Filling and Electron Confinement at the LaAlO$_{3}$-SrTiO$_{3}$ Interface},
author = {A. E. M. Smink and M. P. Stehno and J. C. de Boer and A. Brinkman and W. G. van der Wiel and H. Hilgenkamp},
journal= {arXiv preprint arXiv:1801.02881},
year = {2018}
}