Influence of oxygen vacancies on two-dimensional electron systems at SrTiO3-based interfaces and surfaces

Sing, M.; Jeschke, Harald O.; Lechermann, Frank; Valentí, Roser; Claessen, R.

doi:10.1140/epjst/e2017-70059-7

Cited by 22 publications

(27 citation statements)

References 105 publications

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“…These states determine the interfacial ferromagnetism of OD-LAO/STO [23,24]. This theoretical picture of the dichotomic electron system formed at the OD-LAO/STO interface [25][26][27][28] has recently been experimentally confirmed by resonant photoemission (ResPE) experiments [29]. The coexistence of the two radically different MES and IGS electron subsystems much enriches the physics of the OD-LAO/STO interfaces compared to the stoichiometric ones.…”

Section: Introductionmentioning

confidence: 76%

“…This observation still has to be fully understood, although a few theoretical works have demonstrated that properties of the V O s depend on their concentration regime [21,46]. An ARPES study of the EPS at the bare STO(100) and (111) surfaces [16,28] has presented evidence that this phenomenon is driven by clustering of V O s. Indeed, local-density approximation (LDA) +U calculations on bare STO surfaces [21,46] suggest that the electron distribution between the MES and IGSs may depend on particular configurations of V O s; while isolated V O s on the surface tend to donate both released electrons into the MES, their cluster configurations favor even distribution. We note that the intensity evolution of the ARPES spectral structures under x-ray irradiation is accompanied by their energy shifts (see Supplemental Material 1 [35]).…”

Section: A X-ray Irradiation Dynamicsmentioning

confidence: 99%

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Electronic phase separation at LaAlO3/SrTiO3 interfaces tunable by oxygen deficiency

Strocov

Chikina

Caputo

et al. 2019

Phys. Rev. Materials

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Electronic phase separation is crucial for the fascinating macroscopic properties of the LaAlO 3 /SrTiO 3 (LAO/STO) paradigm oxide interface, including the coexistence of superconductivity and ferromagnetism. We investigate this phenomenon using angle-resolved photoelectron spectroscopy (ARPES) in the soft-x-ray energy range, where the enhanced probing depth combined with resonant photoexcitation allow us access to fundamental electronic structure characteristics-momentum-resolved spectral function, dispersions and ordering of energy bands, Fermi surface-of buried interfaces. Our experiment uses x-ray irradiation of the LAO/STO interface to tune its oxygen deficiency, building up a dichotomic system where mobile weakly correlated Ti t 2g electrons coexist with localized strongly correlated Ti e g ones. The ARPES spectra dynamics under x-ray irradiation shows a gradual intensity increase under constant Luttinger count of the Fermi surface. This fact identifies electronic phase separation (EPS) where the mobile electrons accumulate in conducting puddles with fixed electronic structure embedded in an insulating host phase, and allows us to estimate the lateral fraction of these puddles. We discuss the physics of EPS invoking a theoretical picture of oxygen-vacancy clustering, promoted by the magnetism of the localized Ti e g electrons, and repelling of the mobile t 2g electrons from these clusters. Our results on the irradiation-tuned EPS elucidate the intrinsic one taking place at the stoichiometric LAO/STO interfaces.

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Section: Introductionmentioning

confidence: 76%

Section: A X-ray Irradiation Dynamicsmentioning

confidence: 99%

Electronic phase separation at LaAlO3/SrTiO3 interfaces tunable by oxygen deficiency

Strocov

Chikina

Caputo

et al. 2019

Phys. Rev. Materials

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“…Here we considered only spin and charge neutral vacancies; however, there is an interesting physics underlying F centers (anionic vacancies) [50]. With the advent of modern thinfilm technology, targeted manipulation and control of defects, in particular at their two-dimensional surfaces and interfaces, has become possible [51]. Moreover, theoretical investigation of defects is critical to understanding the electronic properties of semiconducting compounds [52].…”

Section: Discussionmentioning

confidence: 99%

Effects of vacancies on high-order harmonic generation in a linear chain with band gap

Iravani

Hansen

Madsen

2020

Phys. Rev. Research

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High-order harmonic generation (HHG) in imperfect lattices with point defect vacancies is studied using a self-consistent time-dependent density-functional approach for a one-dimensional linear chain with a band gap. Compared with a perfect lattice with no vacancies, the HHG yield decreases by increasing the number of evenly distributed vacancies but remains almost unchanged in the case when vacancies are localized at neighboring lattice points. By introducing atomic-type point vacancies in the linear chain, it is effectively partitioned into several subsystems and the overall shape of HHG spectra of the resulting system can be modeled via the HHG of its subsystems provided each subsystem is large enough to behave like a bulk solid. For sufficiently small subsystems, the HHG spectra show detectable signatures of finite structure but maintains the overall structure of the spectrum of a bulk solids. A time-frequency profile of the emitted harmonics shows less regular sinusoidal patterns in the systems with vacancies compared with the perfect lattice. The role the vacancy-induced defectstate orbitals in the HHG process is investigated for different realizations of the linear chain and laser parameters.

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“…A similar situation seems to be present in other transition metal oxides like SrTiO 3 83 and its interfaces. 84,85 Furthermore, extrinsic loss that can be large for plasmonic satellites 86 , is not included in our calculations. We propose that the difference in spectral weight between the photoemssion experiments and our ab initio results in the inset of Fig.…”

Section: Spectral Functionsmentioning

confidence: 99%

Multitier self-consistent GW+EDMFT

Nilsson

Boehnke

Werner

et al. 2017

Phys. Rev. Materials

102

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We discuss a parameter-free and computationally efficient ab initio simulation approach for moderately and strongly correlated materials, the multitier self-consistent GW +EDMFT method. This scheme treats different degrees of freedom, such as high-energy and low-energy bands, or local and nonlocal interactions, within appropriate levels of approximation, and provides a fully self-consistent description of correlation and screening effects in the solid. The ab initio input is provided by a one-shot G 0 W 0 calculation, while the strong-correlation effects originating from narrow bands near the Fermi level are captured by a combined GW plus extended dynamical mean-field (EDMFT) treatment. We present the formalism and technical details of our implementation and discuss some general properties of the effective EDMFT impurity action. In particular, we show that the retarded impurity interactions can have non-causal features, while the physical observables, such as the screened interactions of the lattice system, remain causal. As a first application, we present ab initio simulation results for SrMoO3, which demonstrate the existence of prominent plasmon satellites in the spectral function not obtainable within LDA+DMFT, and provide further support for our recent re-interpretation of the satellite features in the related cubic perovskite SrVO3. We then turn to stretched sodium as a model system to explore the performance of the multitier self-consistent GW +EDMFT method in situations with different degrees of correlation. While the results for the physical lattice spacing a0 show that the scheme is not very accurate for electron-gas like systems, because nonlocal corrections beyond GW are important, it does provide physically correct results in the intermediate correlation regime, and a Mott transition around a lattice spacing of 1.5a0. Remarkably, even though the Wannier functions in the stretched compound are less localized, and hence the bare interaction parameters are reduced, the self-consistently computed impurity interactions show the physically expected trend of an increasing interaction strength with increasing lattice spacing.

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Influence of oxygen vacancies on two-dimensional electron systems at SrTiO3-based interfaces and surfaces

Cited by 22 publications

References 105 publications

Electronic phase separation at LaAlO3/SrTiO3 interfaces tunable by oxygen deficiency

Electronic phase separation at LaAlO3/SrTiO3 interfaces tunable by oxygen deficiency

Effects of vacancies on high-order harmonic generation in a linear chain with band gap

Multitier self-consistent GW+EDMFT

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