Band gaps and electronic structure of alkaline-earth and post-transition-metal oxides

McLeod, John A.; Wilks, Regan G.; Skorikov, N. A.; Finkelstein, L. D.; Abu-Samak, M.; Kurmaev, E.Z.; Moewes, A.

doi:10.1103/physrevb.81.245123

Cited by 88 publications

(69 citation statements)

References 73 publications

(36 reference statements)

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“…In Bi-2212, the prominent PG in the BiO(I) layer hampers a direct visualization of the VHS in the underlying SrO(I) layer. Since the VHS develops only after the Bi-2212 samples were annealed to recover superconductivity under the ozone flux, we argue that it might most probably originate from the interstitial oxygen dopants in the SrO(I) layer [19,20], which shift the valance band of insulating SrO upwards to the E F [21]. Nevertheless, the metallic nature of SrO(I) layer leaves little possibility that the PG observed on BiO(I) has a simple root at the subsurface CuO 2 layer due to a missing of VHS around E F on BiO(I).…”

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confidence: 99%

Mapping the Electronic Structure of Each Ingredient Oxide Layer of High-TcCuprate SuperconductorBi2Sr2<

Lv¹,

Wang²,

Peng³

et al. 2015

Phys. Rev. Lett.

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Understanding the mechanism of high transition temperature (Tc) superconductivity in cuprates has been hindered by the apparent complexity of their multilayered crystal structure. Using a cryogenic scanning tunneling microscopy, we report on layer-by-layer probing of the electronic structures of all ingredient planes (BiO, SrO, CuO2) of Bi2Sr2CaCu2O 8+δ superconductor prepared by argonion bombardment and annealing technique. We show that the well-known pseudogap (PG) feature observed by STM is inherently a property of the BiO planes and thus irrelevant directly to Cooper pairing. The SrO planes exhibit an unexpected Van Hove singularity near the Fermi level, while the CuO2 planes are exclusively characterized by a smaller gap inside the PG. The small gap becomes invisible near Tc, which we identify as the superconducting gap. The above results constitute severe constraints on any microscopic model for high Tc superconductivity in cuprates.PACS numbers: 74.72. Gh, 68.37.Ef, 74.50.+r, 74.25.Jb Superconductivity in perovskite-type layered cuprates [1], which thus far hold the record for the highest transition temperature (T c ), ranks among the most challenging and engaging problems in modern condensed matter physics. Despite nearly three decades' tremendous efforts of research all around the world, the key mechanism behind the Cooper pairing that lies at the heart of high-T c cuprate superconductors still remains puzzling. Many intriguing phenomena that intertwine with the occurrence of superconductivity have been discovered, leading to a very sophisticated phase diagram of cuprates [2]. These phenomena include the ubiquitous existence of various sorts of broken-symmetry states (e.g. charge density wave, spin density wave and electron nematicity) and the well-known pseudogap (PG) phenomenology, which has been considered a key finding in the research of cuprate superconductivity. A vast amount of experimental and theoretical studies have been devoted to understanding these phenomena themselves and their possible interplay with superconductivity, but so far most of which fell flat.From the view point of crystal structure, the cuprates consist of superconducting CuO 2 layers and charge reservoir building blocks (e.g. BiO/SrO in Bi 2 Sr 2 CaCu 2 O 8+δ (Bi-2212)) that stack alternatively along the crystallographic c-axis. In Bi-based cuprate superconductors, it is widely thought but empirical that the BiO and SrO block layers are insulating [3]. A considerable amount of surface-sensitive measurements, e.g. via angle-resolved photoemission spectroscopy (ARPES) [4] and scanning tunneling spectroscopy (STS) [5], have been conducted on the vacuum cleaved BiO planes of Bi-based cuprates and contributed largely to the cuprate PG data base. The measurements are generally assumed to reflect the superconducting properties of the CuO 2 planes, despite that they are located 4.5Å beneath the top BiO plane. Yet, such model has not been rigidly tested experimentally thus appears contentious, particularly regarding to the fact tha...

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confidence: 99%

Mapping the Electronic Structure of Each Ingredient Oxide Layer of High-TcCuprate SuperconductorBi2Sr2<

Lv¹,

Wang²,

Peng³

et al. 2015

Phys. Rev. Lett.

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“…This shows Mg co-ordination to be almost the same, both at the surface and in the volume of the film. The measured O K-edge NEXAFS X-Ray Absorption Near Edge Structure (XANES) spectra [40,[90][91][92][93][94] of the film detected by TEY and TFY [95] modes are shown in Figure 8b. According to electronic structure calculation the spectral features B1, B2, B3, B 4 and B5 in the energy range of 80 eV above threshold arise from multiple scattering resonances in the energy of the excited The measured O K-edge NEXAFS spectra [40,[90][91][92][93][94] of the film detected by TEY and TFY [95] modes are shown in Figure 8b.…”

Section: Condens Matter 2017 2 36mentioning

confidence: 99%

“…The measured O K-edge NEXAFS X-Ray Absorption Near Edge Structure (XANES) spectra [40,[90][91][92][93][94] of the film detected by TEY and TFY [95] modes are shown in Figure 8b. According to electronic structure calculation the spectral features B1, B2, B3, B 4 and B5 in the energy range of 80 eV above threshold arise from multiple scattering resonances in the energy of the excited The measured O K-edge NEXAFS spectra [40,[90][91][92][93][94] of the film detected by TEY and TFY [95] modes are shown in Figure 8b. According to electronic structure calculation the spectral features B 1 , B 2 , B 3 , B 4 and B 5 in the energy range of 80 eV above threshold arise from multiple scattering resonances in the energy of the excited photoelectron in Mg and O states with p symmetry [40,90,92].…”

Section: Condens Matter 2017 2 36mentioning

confidence: 99%

“…According to electronic structure calculation the spectral features B1, B2, B3, B 4 and B5 in the energy range of 80 eV above threshold arise from multiple scattering resonances in the energy of the excited The measured O K-edge NEXAFS spectra [40,[90][91][92][93][94] of the film detected by TEY and TFY [95] modes are shown in Figure 8b. According to electronic structure calculation the spectral features B 1 , B 2 , B 3 , B 4 and B 5 in the energy range of 80 eV above threshold arise from multiple scattering resonances in the energy of the excited photoelectron in Mg and O states with p symmetry [40,90,92]. Rectangular region in Figure 8b shows pre-edge structures, which arises due to the excitation to the localized bound state and presence of surface state or intermixing [92,96] as it is common to occur in the NEXAFS spectra of metal oxides.…”

Section: Condens Matter 2017 2 36mentioning

confidence: 99%

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d° Ferromagnetism of Magnesium Oxide

Singh

Chae

2017

Condensed Matter

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Magnetism without d-orbital electrons seems to be unrealistic; however, recent observations of magnetism in non-magnetic oxides, such as ZnO, HfO 2 , and MgO, have opened new avenues in the field of magnetism. Magnetism exhibited by these oxides is known as d • ferromagnetism, as these oxides either have completely filled or unfilled d-/f-orbitals. This magnetism is believed to occur due to polarization induced by p-orbitals. Magnetic polarization in these oxides arises due to vacancies, the excitation of trapped spin in the triplet state. The presence of vacancies at the surface and subsurface also affects the magnetic behavior of these oxides. In the present review, origins of magnetism in magnesium oxide are discussed to obtain understanding of d • ferromagnetism.

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“…2) infers that lattice constant of SrO film is almost perfectly matched with Sr 3 PbO film (experimental mismatch ∼0.2% evaluated from (002) reflections). Strontium oxide is an insulator with a large band gap of 6.1 eV, 31 which is ideal as a barrier layer. Therefore, it would be an interesting future work to create a multilayer of Sr 3 PbO and SrO, particularly pertaining to recent theoretical proposal to induce novel topological states via artificial structure.…”

Section: -6mentioning

confidence: 99%

Molecular beam epitaxy of three-dimensional Dirac material Sr3PbO

2016

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A series of anti-perovskites including Sr3PbO are recently predicted to be a three-dimensional Dirac material with a small mass gap, which may be a topological crystalline insulator. Here, we report the epitaxial growth of Sr3PbO thin films on LaAlO3 using molecular beam epitaxy. X-ray diffraction indicates (001) growth of Sr3PbO, where [110] of Sr3PbO matches [100] of LaAlO3. Measurements of the Sr3PbO films with parylene/Al capping layers reveal a metallic conduction with p-type carrier density of ∼1020 cm−3. The successful growth of high quality Sr3PbO film is an important step for the exploration of its unique topological properties.

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Band gaps and electronic structure of alkaline-earth and post-transition-metal oxides

Cited by 88 publications

References 73 publications

Mapping the Electronic Structure of Each Ingredient Oxide Layer of High-TcCuprate SuperconductorBi2Sr2<

Mapping the Electronic Structure of Each Ingredient Oxide Layer of High-TcCuprate SuperconductorBi2Sr2<

d° Ferromagnetism of Magnesium Oxide

Molecular beam epitaxy of three-dimensional Dirac material Sr3PbO

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