Two-Dimensional Confinement of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>3</mml:mn><mml:msup><mml:mi>d</mml:mi><mml:mn>1</mml:mn></mml:msup></mml:math>Electrons in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>LaTiO</mml:mi><mml:mn>3</mml:mn></mml:msub><mml:mo>/</mml:mo><mml:msub><mml:mi>LaAlO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>Multilayers

Seo, S. S. A.; Han, Myung Joon; Hassink, G.W.J.; Choi, Woo Seok; Moon, Seok‐Jun; Kim, J. S.; Susaki, Tomofumi; Lee, Y. S.; Yu, Jingkun; Bernhard, C.; Hwang, Harold Y.; Rijnders, Guus; Blank, Dave H.A.; Keimer, B.; Noh, T. W.

doi:10.1103/physrevlett.104.036401

Cited by 41 publications

(10 citation statements)

References 31 publications

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“…The XLD signal is enhanced with decreasing n from 10 to 2. Such anisotropy in the e g orbitals manifests ‘lifting' of the 3 z 2 - r 2 level under low dimensionality58121823. The energy difference between the 3 z 2 - r 2 state and the x 2 - y 2 state is estimated to be ∼1 eV, which is very close to the energy distance between the leading peak positions in the unoccupied 3 z 2 - r 2 and x 2 - y 2 DOS in the DMFT result (see Figure 2b).…”

Section: Discussionsupporting

confidence: 52%

“…In particular, the quantum confinement effect can selectively increase the energy of orbitals concentrated along the z direction (3 z 2 - r 2 and xz/yz ). Moreover, in heterostructures with a spacer layer such as LAO, certain chemical interactions at the interface between the LCO layer and the spacer layer can influence the strength of the Co 3 d (3 z 2 - r 2 )-O 2 p hybridization3818. Such interactions can affect the total energy of the HS state while keeping the total energy of the LS state almost unchanged.…”

Section: Resultsmentioning

confidence: 99%

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Dimensionality Control of d-orbital Occupation in Oxide Superlattices

Jeong

Choi

Okamoto

et al. 2014

Sci Rep

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Manipulating the orbital state in a strongly correlated electron system is of fundamental and technological importance for exploring and developing novel electronic phases. Here, we report an unambiguous demonstration of orbital occupancy control between t2g and eg multiplets in quasi-two-dimensional transition metal oxide superlattices (SLs) composed of a Mott insulator LaCoO3 and a band insulator LaAlO3. As the LaCoO3 sublayer thickness approaches its fundamental limit (i.e. one unit-cell-thick), the electronic state of the SLs changed from a Mott insulator, in which both t2g and eg orbitals are partially filled, to a band insulator by completely filling (emptying) the t2g (eg) orbitals. We found the reduction of dimensionality has a profound effect on the electronic structure evolution, which is, whereas, insensitive to the epitaxial strain. The remarkable orbital controllability shown here offers a promising pathway for novel applications such as catalysis and photovoltaics, where the energy of d level is an essential parameter.

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Section: Discussionsupporting

confidence: 52%

Section: Resultsmentioning

confidence: 99%

Dimensionality Control of d-orbital Occupation in Oxide Superlattices

Jeong

Choi

Okamoto

et al. 2014

Sci Rep

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“…11 Due to the large crystal field splitting at the LaTiO 3 /LAO interface, a 2DEG can also be created in LaTiO 3 . 12 In this paper, we focus on a somewhat different phenomenon that can be realized in heterostructures of transition metal oxides: the creation of quantum well (QW) states. 13 QW states appear when a thin material with a smaller band gap is sandwiched between two materials with wider band gaps, with the band alignment confining the electron motion along the stacking direction.…”

Section: Introductionmentioning

confidence: 99%

Optical properties of transition metal oxide quantum wells

Lin

Posadas

Choi

et al. 2015

Journal of Applied Physics

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Fabrication of a quantum well, a structure that confines the electron motion along one or more spatial directions, is a powerful method of controlling the electronic structure and corresponding optical response of a material. For example, semiconductor quantum wells are used to enhance optical properties of laser diodes. The ability to control the growth of transition metal oxide films to atomic precision opens an exciting opportunity of engineering quantum wells in these materials. The wide range of transition metal oxide band gaps offers unprecedented control of confinement while the strong correlation of d-electrons allows for various cooperative phenomena to come into play. Here, we combine density functional theory and tight-binding model Hamiltonian analysis to provide a simple physical picture of transition metal oxide quantum well states using a SrO/ SrTiO 3 /SrO heterostructure as an example. The optical properties of the well are investigated by computing the frequency-dependent dielectric functions. The effect of an external electric field, which is essential for electro-optical devices, is also considered. V C 2015 AIP Publishing LLC.

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“…The typical probing depth of these spectroscopic techniques is 5-10 nm. A direct standard (linear) optical spectroscopy of the LAO/STO single interface has also been carried out [21], but its interpretation is obviously hindered by the dominance of the bulk signal, since both LaAlO 3 and SrTiO 3 are wide-gap transparent crystals and their penetration depth at optical frequencies is very large. A more effective way to achieve interface-specific sensitivity approaching a single-monolayer depth is based instead on exploiting the symmetry breaking occurring at the interface, as can be obtained by using second-order nonlinear optics.…”

Section: Introductionmentioning

confidence: 99%

Optical second-harmonic generation selection rules and resonances in buried oxide interfaces: the case of LaAlO_3/SrTiO_3

Paparo¹,

Rubano²,

Marrucci³

2013

J. Opt. Soc. Am. B

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Despite an intense research effort, the physical mechanism underlying the formation of a quasi-two-dimensional electron gas at the interface between the band insulators LaAlO 3 and SrTiO 3 is still not fully understood. Interfacesensitive optical second-harmonic spectroscopy can shed light on this mechanism, by accessing specific information on the orbital and structural reconstruction taking place at the interface that is not accessible by other techniques, and in particular by transport measurements. Here we present a detailed theoretical analysis of the spectral transitions that are most relevant in the second-order nonlinear optical response of oxide interfaces with a square symmetry, in general. In particular, we discuss the case of LaAlO 3 ∕SrTiO 3 interfaces, using symmetry arguments to derive specific selection rules, which have strong consequences on the second-harmonic spectra recorded with different input/output polarization combinations of light. These selection rules may in particular explain recent experimental findings.

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Two-Dimensional Confinement of3d1Electrons inLaTiO3/LaAlO3Multilayers

Cited by 41 publications

References 31 publications

Dimensionality Control of d-orbital Occupation in Oxide Superlattices

Dimensionality Control of d-orbital Occupation in Oxide Superlattices

Optical properties of transition metal oxide quantum wells

Optical second-harmonic generation selection rules and resonances in buried oxide interfaces: the case of LaAlO_3/SrTiO_3

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