Mechanisms of charge transfer and redistribution in LaAlO3/SrTiO3 revealed by high-energy optical conductivity

Asmara, Teguh Citra; Annadi, Anil; Santoso, Iman; Gogoi, Pranjal Kumar; Kotlov, A.; Omer, Humair; Motapothula, M.; Breese, Mark B. H.; Rübhausen, Michael; Venkatesan, T.; Ariando, Ariando; Rusydi, Andrivo

doi:10.1038/ncomms4663

Cited by 73 publications

(117 citation statements)

References 57 publications

(186 reference statements)

Supporting

Mentioning

100

Contrasting

Order By: Relevance

“…Band structure studies imply that the lattice distortion due to ionic relaxations are more at the outer layers of LaAlO 3 film that are adjacent to the SrTiO 3 and to the air; the distortion decreases and eventually vanishes as the thickness of LaAlO 3 is increased [22,23]. Further the electron carrier density measured by optical conductivity studies was found to agree with the value predicted by PCM [20,21], which supports the validity of PCM.…”

Section: Polar Catastrophe Model (Pcm)supporting

confidence: 76%

“…However, there exists a threshold thickness (3 unit cells) of LaAlO 3 , above which the metallic conductivity was observed [2,19]. From optical studies, it was shown that up to the thickness of 3 unit cells, the transferred electrons are trapped in the localized states of interface created by lattice distortion [20,21]. Band structure studies imply that the lattice distortion due to ionic relaxations are more at the outer layers of LaAlO 3 film that are adjacent to the SrTiO 3 and to the air; the distortion decreases and eventually vanishes as the thickness of LaAlO 3 is increased [22,23].…”

Section: Polar Catastrophe Model (Pcm)mentioning

confidence: 99%

See 1 more Smart Citation

Charge fractionalization in oxide heterostructures: A field-theoretical model

Selvan

Panigrahi

2016

EPL

View full text Add to dashboard Cite

LaAlO3/SrTiO3 heterostructure with polar and non-polar constituents has been shown to exhibit interface metallic conductivity due to fractional charge transfer to the interface. The interface reconstruction by electron redistribution along (001) orientation, in which half of an electron is transferred per two dimensional unit cell to the adjacent planes, resulting in a net transfer of half of the charge, to both the interface and top most atomic planes, has been ascribed to a polar discontinuity at the interface in the Polar Catastrophe model. This avoids the divergence of electrostatic potential, as the number of layers are increased, producing an oscillatory electric field and finite potential. Akin to the description of charge fractionalization in quasi one-dimensional polyacetylene by the field theoretic Jackiw-Rebbi model with fermions interacting with topologically non-trivial background field, we show an analogous connection between polar catastrophe model and Bell-Rajaraman model, where the charge fractionalization occurs in the soliton free sector as an end effect.

show abstract

Section: Polar Catastrophe Model (Pcm)supporting

confidence: 76%

Section: Polar Catastrophe Model (Pcm)mentioning

confidence: 99%

Charge fractionalization in oxide heterostructures: A field-theoretical model

Selvan

Panigrahi

2016

EPL

View full text Add to dashboard Cite

show abstract

“…Reinterpretation of the puzzle: According to Gauss' law, the experimentally observed weak electric field in LaAlO 3 film means that the total external charge density (mobile and/or immobile) at the interface must be B0.5e S 2D À 1 (Supplementary Note 7), as recently observed 55 . For n LAO oL c , there is no interfacial conductivity and thus none of these interfacial charge contribute to the conductivity.…”

Section: Articlementioning

confidence: 94%

A polarity-induced defect mechanism for conductivity and magnetism at polar–nonpolar oxide interfaces

2014

View full text Add to dashboard Cite

The discovery of conductivity and magnetism at the polar-nonpolar interfaces of insulating nonmagnetic oxides such as LaAlO 3 and SrTiO 3 has raised prospects for attaining interfacial functionalities absent in the component materials. Yet, the microscopic origin of such emergent phenomena remains unclear, posing obstacles to design of improved functionalities. Here we present first principles calculations of electronic and defect properties of LaAlO 3 / SrTiO 3 interfaces and reveal a unifying mechanism for the origins of both conductivity and magnetism. We demonstrate that the polar discontinuity across the interface triggers thermodynamically the spontaneous formation of certain defects that in turn cancel the polar field induced by the polar discontinuity. The ionization of the spontaneously formed surface oxygen vacancy defects leads to interface conductivity, whereas the unionized Ti-on-Al antisite defects lead to interface magnetism. The proposed mechanism suggests practical design principles for inducing and controlling both conductivity and magnetism at general polar-nonpolar interfaces.

show abstract

“…Most groups assume the surface to be AlO 2 -terminated by counting RHEED intensity oscillations during growth. 12,20 However, the surface termination and its structure may change upon exposure to conditions under which the 2DEG properties are measured.…”

Section: Introductionmentioning

confidence: 99%

First-principles study of surface charging inLaAlO3/SrTiO3heterostructures

et al. 2015

View full text Add to dashboard Cite

The two-dimensional electron gas (2DEG) observed at the interface between LaAlO3 (LAO) and SrTiO3 (STO) is known to be very sensitive to the proximity of the LaAlO3 surface and the conditions to which the surface is exposed. We use first-principles calculations to study surface reconstructions on LAO films, taking into account that the LAO surface can be charged. The results for the charged surfaces and for the coupling between the surface and the 2DEG enable us to account not only for the behavior of the 2DEG as a function of thickness of the LAO layer, but simultaneously determine the stable terminations and reconstructions on the LAO surface under a variety of conditions. Our studies of charged surfaces are based on an extension of the methodology of Lozovoi et al. [J. Chem. Phys. 115, 1661(2001]. From the calculated electronic structure of the unreconstructed (but relaxed) AlO2 and LaO surface terminations of LAO, we find surface states having excess holes (AlO2 termination) or excess electrons (LaO termination). This result is central to understanding the mechanism of 2DEG formation, and is consistent with a 2DEG of density 3.3×10 14 cm −2 being intrinsic to the LaO-TiO2 interface in the LAO/STO system. We explore the effects of the Al-adatom, O-vacancy and H-adatom surface reconstructions on the 2DEG density, and find that the stability of different reconstructions is tied to the thickness of the LAO layer as well as the surface exposure conditions. We find that including the effects of charging of the surface significantly stabilizes the AlO2 termination versus the LaO termination. Overall, our methodology has the advantage of decoupling first-principles calculations for the interface from those for the charged surface, and constitutes a general approach that can be applied to the commonly occurring problem of charge exchange between the surface and the interface of a thin film with a substrate, or between the surface and defects/impurities in the bulk of a material.

show abstract

Mechanisms of charge transfer and redistribution in LaAlO3/SrTiO3 revealed by high-energy optical conductivity

Cited by 73 publications

References 57 publications

Charge fractionalization in oxide heterostructures: A field-theoretical model

Charge fractionalization in oxide heterostructures: A field-theoretical model

A polarity-induced defect mechanism for conductivity and magnetism at polar–nonpolar oxide interfaces

First-principles study of surface charging inLaAlO3/SrTiO3heterostructures

Contact Info

Product

Resources

About