Strong correlations elucidate the electronic structure and phase diagram of LaAlO3/SrTiO3 interface

Maniv, Eran; Shalom, M. Ben; Ron, Amos; Mograbi, M.; Palevski, A.; Goldstein, Moshe; Dagan, Y.

doi:10.1038/ncomms9239

Cited by 68 publications

(100 citation statements)

References 37 publications

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“…This interpretation that the lower d xy band is the cradle of attractive interactions is consistent with the measurement at the 2D LAO=STO interface, which shows that the optimal doping for superconductivity happens at the Liftshitz transition [33]. We note that an alternative description of phenomena ascribed to the Lifshitz transition has been presented by Maniv et al [34], who ascribe the onset of superconductivity as arising from population of the d xz =d yz bands and interactions within those bands that map out the superconducting dome.…”

Section: Mechanisms For Density-tuned Interactions-lifshitz Transsupporting

confidence: 74%

Tunable Electron-Electron Interactions inLaAlO3/SrTiO3Nanostructures

et al. 2016

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The interface between the two complex oxides LaAlO 3 and SrTiO 3 has remarkable properties that can be locally reconfigured between conducting and insulating states using a conductive atomic force microscope. Prior investigations of "sketched" quantum dot devices revealed a phase in which electrons form pairs, implying a strongly attractive electron-electron interaction. Here, we show that these devices with strong electron-electron interactions can exhibit a gate-tunable transition from a pair-tunneling regime to a singleelectron (Andreev bound state) tunneling regime where the interactions become repulsive. The electronelectron interaction sign change is associated with a Lifshitz transition where the d xz and d yz bands start to become occupied. This electronically tunable electron-electron interaction, combined with the nanoscale reconfigurability of this system, provides an interesting starting point towards solid-state quantum simulation.

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Section: Mechanisms For Density-tuned Interactions-lifshitz Transsupporting

confidence: 74%

Tunable Electron-Electron Interactions inLaAlO3/SrTiO3Nanostructures

et al. 2016

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“…The redistribution of carriers to the d yz;xz bands can thus not be explained by interaction of the potential well and the band structure alone, but has to be mediated by an effect not yet included in the calculations. As recently reported by Maniv et al [49], electronic correlations can mediate such a redistribution of carriers.…”

mentioning

confidence: 71%

“…We model these correlations as repulsive electronelectron interactions, with an interaction term E i int ¼ P n j¼1 Uð1 − δ ij =2ÞN j , for each band i [49]. Here, N j is the 2D electron density per unit cell of band j, δ ij is the Kronecker delta, and U is the phenomenological screened Coulomb interaction strength between bands, which we take equal for all bands for simplicity.…”

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confidence: 99%

Gate-Tunable Band Structure of the LaAlO3−SrTiO3 Interface

et al. 2017

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The two-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 Schrödinger-Poisson calculations and observe a Lifshitz transition at a density of 2.9 × 10 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. DOI: 10.1103/PhysRevLett.118.106401 The two-dimensional electron system (2DES) at the interface between the band insulators LaAlO 3 (LAO) and SrTiO 3 (STO) displays many intriguing phenomena, which may be harnessed for novel electronic devices [1][2][3][4][5]. The discovery of superconductivity [6], magnetic signatures [7][8][9][10], and their apparent coexistence [11] sparked growing interest in this material system. These properties can be tuned by varying parameters during growth [4,7], as well as by an externally applied electric field after growth [12]. Using this field effect, control of superconductivity [13][14][15][16][17], of spin-orbit coupling [17][18][19][20], and of carrier mobility [21,22] has been reported. Recent progress on local control of superconductivity [16] opened a route towards electrically controlled oxide Josephson junctions [23,24], providing new opportunities for superconducting electronic devices. Because these phenomena are related to the interfacial band structure, a fundamental understanding of the band structure is vital for the understanding of these phenomena and their exploitation in electronic devices.The interface band structure is formed by the conduction band of STO, which is bent down at the interface and crosses the Fermi level [25]. The origin of the band bending is still an open question [26][27][28]. This band bending creates a potential well, confining the carriers to a few nanometers in the out-of-plane direction [29][30][31][32]. In the well, the effective band structure is formed by the Ti t 2g orbitals. For interfaces grown along the [001] direction, the in-plane oriented d xy bands lie below the out-of-plane oriented d yz;xz bands in energy due to the confinement, as measured using x-ray absorption [33].By backgating the interface through the STO substrate, an additional conduction channel was observed to emerge above a carrier density of ð1.7 AE 0.1Þ × 10 13 cm −2 [34]. This observation was linked to tuning the Fermi level across the bottom of the d yz;xz bands, making additional electron pockets available for conduction. As a result, the Fermi surface topology changes, which is the characteristic feature of a Lifshitz transition [35].The model proposed by Joshua et...

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“…Carriers are confined within a thickness of typically 10 nm at low temperature [1,8,[12][13][14], which causes quantum confinement to an effective two-dimensional electron liquid (2DEL). Hartree shifts in the 3d shell affect the band structure [15], and Rashba coupling at the interface may mix singlet and triplet pairing channels [5,16]. The superfluid density in the 2DEL is much lower than the normal-state Hall density, [11,17] suggesting that 2D fluctuations influence the superconducting properties [8,18].…”

Section: Introductionmentioning

confidence: 99%

“…Second, an increase in the splitting E is expected at the interface, since both strain and electric field contribute directly to the fourfold crystal field. A modified screening also modifies the Hartree shifts of the bands [15]. We adopt the simple dependence E = E STO (1 + λ/L) with the fit parameter λ, which ensures that the bulk STO splitting is recovered for a thick well.…”

Section: Critical Temperature Of Sto Carriers Confined In a Squarmentioning

confidence: 99%

Modulation of the superconducting critical temperature due to quantum confinement at the LaAlO3/SrTiO3 interface

et al. 2017

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Superconductivity develops in bulk doped SrTiO 3 and at the LaAlO 3 /SrTiO 3 interface with a dome-shaped density dependence of the critical temperature T c , despite different dimensionalities and geometries. We propose that the T c dome of LaAlO 3 /SrTiO 3 is a shape resonance due to quantum confinement of superconducting bulk SrTiO 3 . We substantiate this interpretation by comparing the exact solutions of a three-dimensional and quasi-two-dimensional two-band BCS gap equation. This comparison highlights the role of heavy bands for T c in both geometries. For bulk SrTiO 3 , we extract the density dependence of the pairing interaction from the fit to experimental data. We apply quantum confinement in a square potential well of finite depth and calculate T c in the confined configuration. We compare the calculated T c to transport experiments and provide an explanation as to why the optimal T c 's are so close to each other in two-dimensional interfaces and the three-dimensional bulk material.

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Strong correlations elucidate the electronic structure and phase diagram of LaAlO3/SrTiO3 interface

Cited by 68 publications

References 37 publications

Tunable Electron-Electron Interactions inLaAlO3/SrTiO3Nanostructures

Tunable Electron-Electron Interactions inLaAlO3/SrTiO3Nanostructures

Gate-Tunable Band Structure of the LaAlO3−SrTiO3 Interface

Modulation of the superconducting critical temperature due to quantum confinement at the LaAlO3/SrTiO3 interface

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