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arXiv · 1110.2184

A Universal Critical Density Underlying the Physics of Electrons at the LaAlO3/SrTiO3 Interface

Arjun Joshua·S. Pecker·J. Ruhman·E. Altman·S. Ilani
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Abstract

The two-dimensional electron system formed at the interface between the insulating oxides LaAlO3 and SrTiO3 exhibits ferromagnetism, superconductivity, and a wide range of unique magnetotransport properties. A key challenge is to find a unified microscopic mechanism that underlies these emergent phenomena. Here we show that a universal Lifshitz transition between d-orbitals lies at the core of the observed transport phenomena in this system. Our measurements find a critical electronic density at which the transport switches from single to multiple carriers. This density has a universal value, independent of the LaAlO3 thickness and electron mobility. The characteristics of the transition, its universality, and its compatibility with spectroscopic measurements establish it as a transition between d-orbitals of different symmetries. A simple band model, allowing for spin-orbit coupling at the atomic level, connects the observed universal transition to a range of reported magnetotransport properties. Interestingly, we also find that the maximum of the superconducting transition temperature occurs at the same critical transition, indicating a possible connection between the two phenomena. Our observations demonstrate that orbital degeneracies play an important role in the fascinating behavior observed so far in these oxides.

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Arjun Joshua, S. Pecker, J. Ruhman, E. Altman, S. Ilani. 2011-10-10. A Universal Critical Density Underlying the Physics of Electrons at the LaAlO3/SrTiO3 Interface. https://doi.org/10.1038/ncomms2116

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