Two dimensional superconductors in electrides

Ge, Yanfeng; Guan, Shaokang; Liu, Yong

doi:10.1088/1367-2630/aa8a2d

Cited by 30 publications

(30 citation statements)

References 43 publications

(50 reference statements)

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“…From this λ , the superconducting transition temperature T c is estimated using McMillan's formula [ 116 ] to be 4.7 K, assuming Coulomb pseudopotential μ * = 0.1. A similar calculation for the Y 2 C monolayer by Ge et al gave λ = 0.53 and T c = 0.9 K. [ 117 ] The calculated phonon linewidths and Eliashberg spectral function α 2 F ( ω ) indicate that the main contribution comes from high‐frequency optical phonons with energy >300 cm −1 . Thus far, there has been no report on the observation of superconductivity in Q2DEs.…”

Section: Miscellaneous Properties Of 2d Electrides and Electrenesmentioning

confidence: 65%

Floating Interlayer and Surface Electrons in 2D Materials: Graphite, Electrides, and Electrenes

2021

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Over the last half century, layered materials have been at the forefront of materials science, spearheading the discovery of new phenomena and functionalities. Certain layered materials are known to possess electronic states unassociated with any of the constituent atoms, having a large proportion of their probability amplitude in the space between the layers. Usually, such a nucleus‐free interlayer state has energy above the Fermi level and is unoccupied. However, the energy decreases when cations are intercalated and may cross the Fermi level, as in the case of C6Ca, a superconductor with a Tc of 11.5 K. A major thrust to the research of interlayer electrons comes with the discovery of layered electrides, which are alternating stacks of positively charged ionic layers and negatively charged sheets of electrons in the interlayer space. When intercalation compounds and layered electrides are thinned down to the atomic scale, the interlayer states survive as surface states floating over the surface. This review provides a unified overview of the two classes of materials hosting interlayer floating electrons near the Fermi level, intercalation compounds and layered electrides, and their properties, including high electron mobility, low work function, ultralow interlayer friction, superconductivity, and plasmonic properties.

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Section: Miscellaneous Properties Of 2d Electrides and Electrenesmentioning

confidence: 65%

Floating Interlayer and Surface Electrons in 2D Materials: Graphite, Electrides, and Electrenes

2021

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“…2D electrides MgONa and CaONa are metallic due to the existence of the bands crossing the Fermi level (see red colored bands in Figures 3c and 3 f). The anionic electrons are confined in interlayer regions with high density as in metals and they behave as free electrons in 2D electrides [28] . Thus, we can anticipate their hyperbolic responses with low losses in shorter wavelength ranges compared with the other strongly anisotropic bulk materials, taking into account that the plasma frequency is proportional to the density of free electrons.…”

Section: Resultsmentioning

confidence: 99%

“…As a special kind of ionic compounds with excess valence electrons playing the role of anions, [23] electrides have recently attracted great attention in the field of materials sciences [24–27] . In 2D electride materials, [28] anionic electrons are spatially confined into the layered regions with high density comparable to metals and are separated from the cations in the crystal, unbound to any lattice site and being freely movable as free electrons. Thus, the electronic structure of 2D electrides resembles hyperbolic metamaterials with metal‐dielectric multilayered structures (see e. g. Ref.…”

Section: Introductionmentioning

confidence: 99%

The Two‐Dimensional Electrides XONa (X=Mg, Ca) as Novel Natural Hyperbolic Materials

Choe

Kim

2020

ChemPhysChem

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In two‐dimensional electrides, anionic electrons are spatially confined in interlayer regions with high density, comparable to metals, and they are highly mobile, just as free electrons, resembling hyperbolic metamaterials with metal‐dielectric multilayered structures. In this work, two‐dimensional electride materials MgONa and CaONa are proposed as good natural hyperbolic materials. By using the first‐principles calculations based on density functional theory (DFT), the electronic structures, stabilities, and optical properties of two‐dimensional electride materials XONa (X=Mg, Ca) are investigated. Our results show that they are stable in 1‐monolayer (1‐ML) structures as well as in bulk states. They exhibit hyperbolic dispersions from visible to near infrared spectral range with high qualities up to about 700, which is two orders‐of‐magnitude larger than the preceding bulk hyperbolic materials. Numerical results reveal that they exhibit negative refraction with low losses. Their high‐quality hyperbolic responses over a wide spectral range pave the way of broad photonic applications as natural hyperbolic materials.

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“…An electride is expected to be a Mott insulator and some electrides are superconductors at low temperatures. 13,[67][68][69] In addition, they also present huge non-linear optical properties (NLOPs), which include some of the largest static first hyperpolarizabilities ever reported. 70,71 However, none of these properties are exclusive of electrides, and one is deemed to measure the most salient feature of electrides: the existence of an isolated electron.…”

Section: Electridementioning

confidence: 99%

How Many Electrons Holds a Molecular Electride?

Sitkiewicz¹,

Ramos‐Cordoba²,

Luis³

et al. 2021

Preprint

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<div> <div> <div> <p>Electrides are very peculiar ionic compounds where electrons occupy the anionic positions. In a crystal lattice, these isolated electrons often group forming channels or surfaces, furnishing electrides with a plethora of traits with promising technological applications. Despite their huge potential, thus far, only a few stable electrides have been produced because of the intricate synthesis they entail. Due to the difficulty in assessing the presence of isolated electrons, the characterization of electrides also poses some serious challenges. In fact, their properties are expected to depend on the arrangement of these electrons in the molecule. Among the criteria that we can use to characterize electrides, the presence of a non-nuclear attractor (NNA) of the electron density is both the rarest and the most salient feature. Therefore, a correct description of the NNA is crucial to determine the properties of electrides. In this paper, we analyze the NNA and the surrounding region of nine molecular electrides with the goal of determining the number of isolated electrons that are held in the electride. We have seen that the correct description of a molecular electride hinges on the electronic structure method employed for the analyses. In particular, one should employ a basis set with sufficient flexibility to describe the region close to the NNA and a density functional approximation that does not suffer from large delocalization errors. Finally, we have classified these nine molecular electrides according to the most likely number of electrons that we can find in the NNA. We believe this classification highlights the strength of the electride character and will prove useful in the design of new electrides.</p> </div> </div> </div>

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Two dimensional superconductors in electrides

Cited by 30 publications

References 43 publications

Floating Interlayer and Surface Electrons in 2D Materials: Graphite, Electrides, and Electrenes

Floating Interlayer and Surface Electrons in 2D Materials: Graphite, Electrides, and Electrenes

The Two‐Dimensional Electrides XONa (X=Mg, Ca) as Novel Natural Hyperbolic Materials

How Many Electrons Holds a Molecular Electride?

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