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 orbital subband structures and chiral orbital angular momentum in the (001) surface states of 
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Soltani, Shoresh; Cho, Soohyun; Ryu, Hanyoung; Han, Gil Soo; Kim, Beomyoung; Song, Dongjoon; Kim, T. K.; Hoesch, Moritz; Kim, Changyoung

doi:10.1103/physrevb.95.125103

Cited by 8 publications

(5 citation statements)

References 49 publications

(70 reference statements)

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“…We note that this value is an underestimate, as it does not account for the decaying electron density profile from the surface, which is known to exist for similar 2DEGs formed at the LAO/STO interface . We further note that while this estimated density is lower than the vacancy‐induced surface 2DEG densities around 1 × 10 14 cm −2 reported in other works, this difference is likely due to the more gradual decay in the oxygen vacancies perpendicular to the surface in our sample. In other STO‐based 2DEGs generated by in situ cleaving/UV light irradiation, oxygen vacancies are mainly confined to the surface unit cells.…”

Section: Resultscontrasting

confidence: 58%

“…From our estimation, 300 meV of band bending with a Fermi level 100 meV below the bulk conduction band minimum indicates the surface 2DEG bandwidth is ≈200 meV. [43] We further note that while this estimated density is lower than the vacancy-induced surface 2DEG densities around 1 × 10 14 cm −2 reported in other works, [27][28][29]44] this difference is likely due to the more gradual decay in the oxygen vacancies perpendicular to the surface in our sample. [27,28,31] We note that a similar behavior has been observed in other orientations of STO, [32] and the seemingly universal band bending behavior merits further investigation.…”

Section: Band-diagram Descriptions Of Oxygen-vacancy-induced Electronsupporting

confidence: 47%

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The Vacancy‐Induced Electronic Structure of the SrTiO_3−δ Surface

Cook

Dylla

Rosenberg

et al. 2018

Adv Elect Materials

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interface was shown to be tunable by an electric-field effect, [10,11] leading to the discovery of gate-tunable exotic properties such as superconductivity, [11][12][13][14] magnetism, [15] and Rashba interaction, [16][17][18] which can be exploited in novel electronic and spintronic devices. [19] The intriguing conductivity arising between LAO and STO-both of which are wide band gap insulators with band gaps of 5.6 and 3.2 eV, respectively-was initially explained by the polar catastrophe model. [4,20] According to this model, a charge of 0.5 e − per square STO lattice parameter is transferred from the LAO surface to the STO side of the interface to prevent the electrical potential from diverging due to the polar stacking of LaO + and AlO 2 − layers. Figure 1a illustrates this behavior, in which a downward bending of STO bands near the interface creates a narrow potential well that accommodates and confines the transferred charge at the interface, forming the 2DEG. However, numerous reports have proposed alternative explanations for the origin of the 2DEG, including charge doping by oxygen vacancies and cation intermixing. [21][22][23][24][25][26] Interestingly, angle-resolved photoemission spectroscopy (ARPES) studies showed that a similar 2DEG can be stabilized on the bare surface of STO (001) cleaved under ultrahigh vacuum (UHV) conditions following ultraviolet (UV)-light irradiation. [27][28][29] The 2DEG in this case is an electron accumulation layer that screens the positively charged oxygen vacancy defects ( O 2 V + or O V ⋅⋅ in Kröger-Vink notation) formed near the surface. The positively charged oxygen vacancies donate charge (e − ) while also inducing downward band bending at the STO surface, providing a confining potential well for the doped electrons. This is illustrated schematically in Figure 1b and also in Figure 1c, where the 2DEG is shown to form from Ti 3d t 2gderived quantized states (subbands).Recent studies have employed a variety of techniques to generate a 2DEG on the STO surface, also based on oxygen vacancy formation, including in situ sputtering, [30] vacuum annealing, [31,32] and metal deposition. [33] However, the quantitative relationship between the surface and bulk electronic structures remains unclear in some of these studies, especially given that n-type conducting (Nb-doped) STO substrates are often used to permit ARPES measurements. [30][31][32] In these The emergence of a 2D electron gas (2DEG) on the (001) surface of oxygendeficient strontium titanate (SrTiO 3−δ ) is investigated. Using in situ soft X-ray spectroscopy and effective mass modeling, a series of quantitative band diagrams are developed to describe the evolution of near-surface and bulk carrier concentrations, downward band bending, and Fermi level along a lateral gradient of oxygen vacancies formed on SrTiO 3−δ by direct-current resistive heating under ultrahigh vacuum conditions. Electrons are accumulated over a 3 nm region near the surface, confined within a potential well with saturated 300 meV downward band be...

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Section: Resultscontrasting

confidence: 58%

Section: Band-diagram Descriptions Of Oxygen-vacancy-induced Electronsupporting

confidence: 47%

The Vacancy‐Induced Electronic Structure of the SrTiO_3−δ Surface

Cook

Dylla

Rosenberg

et al. 2018

Adv Elect Materials

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“…We note that recent results by Soltani et al [53] suggest that a 2D-MES may also be realized at bare STO surfaces. This has been identified from a splitting of the d xz/yz -derived states, suggesting their quantum confinement and thus 2D-ity.…”

Section: Dimensionality Of the Messupporting

confidence: 53%

“…This has been identified from a splitting of the d xz/yz -derived states, suggesting their quantum confinement and thus 2D-ity. Obviously, the dimensionality of the MES is determined by the depth and extension of the surface/interfacial QW which, in turn, is sensitive to the stoichiometry and preparation of the samples, which was in situ cleavage in the experiments by Soltani et al [53] vs in situ annealing in the experiments by Plumb et al [49].…”

Section: Dimensionality Of the Mesmentioning

confidence: 99%

Dimensionality of mobile electrons at x-ray-irradiated LaAlO₃/SrTiO₃ interfaces

et al. 2022

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Electronic structure of LaAlO3/SrTiO3 (LAO/STO) samples, grown at low oxygen pressure and post-annealed ex situ, was investigated by soft-x-ray ARPES focussing on the Fermi momentum (k F) of the mobile electron system (MES). X-ray irradiation of these samples at temperatures below 100 K creates oxygen vacancies (VOs) injecting Ti t 2g-electrons into the MES. At this temperature the oxygen out-diffusion is suppressed, and the VOs should appear mostly in the top STO layer. The x-ray generated MES demonstrates, however, a pronounced three-dimensional (3D) behavior as evidenced by variations of its experimental k F over different Brillouin zones. Identical to bare STO, this behavior indicates an unexpectedly large extension of the x-ray generated MES into the STO depth. The intrinsic MES in the standard LAO/STO samples annealed in situ, in contrast, demonstrates purely two-dimensional (2D) behaviour. The relevance of our ARPES data analysis is supported by model calculations to compare the intensity vs gradient methods of the k F determination as a function of the energy resolution ratio to the bandwidth. Based on self-interaction-corrected DFT calculations of the MES induced by VOs at the interface and in STO bulk, we discuss possible scenarios of the puzzling 3D-ity. It may involve either a dense ladder of quantum-well states formed in a long-range interfacial potential or, more likely, x-ray-induced bulk metallicity in STO accessed in the ARPES experiment through a short-range interfacial barrier. The mechanism of this metallicity may involve remnant VOs and photoconductivity-induced metallic states in the STO bulk, and even more exotic mechanisms such as x-ray induced formation of Frenkel pairs.

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“…The intensity distribution of the photoelectrons depends on the incident polarization, from which the electronic-state information may be disclosed. Recently, it was articulated that the CD pattern in the distribution could be associated with angular-momentum textures [2][3][4][5][6][7][8][9][10][11][12], Berry curvatures [13,14], and degree of surface localization of the wavefunctions [15,16]. CD in ARPES [17][18][19][20] has also been utilized in a variety of ways such as to explore the * ishiday@issp.u-tokyo.…”

Section: Introductionmentioning

confidence: 99%

Classification of the symmetry of photoelectron dichroism broken by light

Ishida,

Chung,

Kwon

et al. 2020

Preprint

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We investigate how the direction of polarized light can affect the dichroism pattern seen in angleresolved photoemission spectroscopy. To this end, we prepared a sample composed of highly-oriented Bi(111) micro-crystals that macroscopically has infinite rotational and mirror symmetry of the point group C∞v and examined whether the dichroism pattern retains the C∞v symmetry under the stationary configuration of the light and sample. The direction of the light was imprinted in the pattern. Thereby, we apply group theory and classify the pattern with the configuration of light taken into account. We complete the classification by discussing the cases when the out-of-plane component of the polarization can be neglected, when the incidence angle is either 0 • or 90 • , when the polarization is either elliptic or linear, and also when the sample is a crystal.

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dxz/yz orbital subband structures and chiral orbital angular momentum in the (001) surface states of SrTiO3

Cited by 8 publications

References 49 publications

The Vacancy‐Induced Electronic Structure of the SrTiO_3−δ Surface

The Vacancy‐Induced Electronic Structure of the SrTiO_3−δ Surface

Dimensionality of mobile electrons at x-ray-irradiated LaAlO₃/SrTiO₃ interfaces

Classification of the symmetry of photoelectron dichroism broken by light

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dxz/yz orbital subband structures and chiral orbital angular momentum in the (001) surface states of SrTiO3

Cited by 8 publications

References 49 publications

The Vacancy‐Induced Electronic Structure of the SrTiO3−δ Surface

The Vacancy‐Induced Electronic Structure of the SrTiO3−δ Surface

Dimensionality of mobile electrons at x-ray-irradiated LaAlO3/SrTiO3 interfaces

Classification of the symmetry of photoelectron dichroism broken by light

Contact Info

Product

Resources

About

The Vacancy‐Induced Electronic Structure of the SrTiO_3−δ Surface

The Vacancy‐Induced Electronic Structure of the SrTiO_3−δ Surface

Dimensionality of mobile electrons at x-ray-irradiated LaAlO₃/SrTiO₃ interfaces