Correlation-Induced Band Competition in SrTiO3/LaAlO3
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Correlation-Induced Band Competition in SrTiO3/LaAlO3 Eran Maniv1, Yoram Dagan1, and Moshe Goldstein1 Raymond and Beverly Sackler School of Physics and Astronomy, Tel Aviv 6997801, Israel
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ABSTRACT The oxide interface SrTiO3/LaAlO3 supports a 2D electron liquid displaying superconductivity and magnetism, while allowing for a continuous control of the electron density using a gate. Our recent measurements have shown a similar surprising nonmonotonic behavior as function of the gate voltage (carrier density) of three quantities: the superconducting critical WHPSHUDWXUH DQG ¿HOG WKH LQYHUVH +DOO FRHIILFLHQW DQG WKH IUHTXHQF\ RI TXDQWXP RVFLOODWLRQV While the total density has to be monotonic as function of gate, the last result indicates that one of the involved bands has a nonmontonic occupancy as function of the chemical potential. We show how electronic interactions can lead to such an effect, by creating a competition between the involved bands and making their sturcture non-rigid, and thus account for all these effects. Adding Fock terms to our pUHYLRXV+DUWUHHWUHDWPHQWPDNHVWKLVVFHQDULReven more generic.
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INTRODUCTION Understanding correlated oxide interfaces is of high importance from both fundamental science perspective and the prospect of future applications [1]. A prime example is the (100) 0.25 2 interface between the insulators SrTiO3 and + c LaAlO3 (STO/LAO) [2]: when the LAO layer is at T c least four unit cells thick, a 2D conducting layer appears between them [3]. The density of electrons 0.2 1.5 in this layers can be easily tuned by a back [3] or top gate [4], similarly to semiconductor 2D electron gas; but, in marked difference from 0.15 semiconductors, the STO/LAO interface shows 1 correlation effects, such as superconductivity [5,6] and magnetism [7,8]. 0.1 Naively, one would expect that upon -5 0 5 10 V g [V] increase of the applied gate voltage Vg, and Figure 1. Nonmonotonic behavior of the superconducting properties (Experiment). The therefore of the carrier density at the interface, the sample measured has 6 unit cells of LAO grown on properties of the system would evolve in a STO as described in ref. [12]. The +DOO-bar monotonic fashion, and it would behave as a dimensions are 9×3 μm2. Left axis (indicated by an progressively better conductor. Surprisingly, this arrow): superconducting critical temperature T C, turns out not to be the case. For example, the defined as the temperature where the resistance drops by 50% with respect to the normal state, vs. superconducting critical temperature Tc DQG ¿HOG back gate voltage (Vg) [squares]. Right axis +c2 ¿UVWJURZEXWWKHQGHFUHDVHDVIXQFWLRQRI9 g (indicated by an arrow): superconducting critical [6,9,10] leading to a dome shape, reminiscent of magnetic field +C2, defined as the magnetic field high-Tc and other exotic superconductors [11] (see where the resistance drops by 50% with respect to Figure 0RUHRYHU WKH LQYHUVH +DOO FRHI¿FLHQW the normal state, vs. Vg at T=60mK [diamonds]. B
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