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تسجيل مستخدم جديدGate-tunable band structure of the LaAlO$_3$-SrTiO$_3$ interface
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The 2-dimensional electron system at the interface between LaAlO$_{3}$ and SrTiO$_{3}$ has several unique properties that can be tuned by an externally applied gate voltage. In this work, we show that this gate-tunability extends to the effective band structure of the system. We combine a magnetotransport study on top-gated Hall bars with self-consistent Schrodinger-Poisson calculations and observe a Lifshitz transition at a density of $2.9times10^{13}$ cm$^{-2}$. Above the transition, the carrier density of one of the conducting bands decreases with increasing gate voltage. This surprising decrease is accurately reproduced in the calculations if electronic correlations are included. These results provide a clear, intuitive picture of the physics governing the electronic structure at complex oxide interfaces.
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Localization of electrons in the two-dimensional electron gas at the LaAlO$_3$/SrTiO$_3$ interface is investigated by varying the channel thickness in order to establish the nature of the conducting channel. Layers of SrTiO$_3$ were grown on NdGaO$_3
$ (110) substrates and capped with LaAlO$_3$. When the SrTiO$_3$ thickness is $leq 6$ unit cells, most electrons at the interface are localized, but when the number of SrTiO$_3$ layers is 8-16, the free carrier density approaches $3.3 times 10^{14}$ cm$^{-2}$, the value corresponding to charge transfer of 0.5 electron per unit cell at the interface. The number of delocalized electrons decreases again when the SrTiO$_3$ thickness is $geq 20$ unit cells. The $sim{4}$ nm conducting channel is therefore located significantly below the interface. The results are explained in terms of Anderson localization and the position of the mobility edge with respect to the Fermi level.
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