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Superconductivity in (Ba,K)SbO₃.

ABSTRACT: (Ba,K)BiO₃ constitute an interesting class of superconductors, where the remarkably high superconducting transition temperature T_c of 30 K arises in proximity to charge density wave order. However, the precise mechanism behind these phases remains unclear. Here, enabled by high-pressure synthesis, we report superconductivity in (Ba,K)SbO₃ with a positive oxygen-metal charge transfer energy in contrast to (Ba,K)BiO₃. The parent compound BaSbO_3-δ shows a larger charge density wave gap compared to BaBiO₃. As the charge density wave order is suppressed via potassium substitution up to 65%, superconductivity emerges, rising up to T_c = 15 K. This value is lower than the maximum T_c of (Ba,K)BiO₃, but higher by more than a factor of two at comparable potassium concentrations. The discovery of an enhanced charge density wave gap and superconductivity in (Ba,K)SbO₃ indicates that strong oxygen-metal covalency may be more essential than the sign of the charge transfer energy in the main-group perovskite superconductors.

SUBMITTER: Kim M

PROVIDER: S-EPMC9156407 | biostudies-literature | 2022 Jun

REPOSITORIES: biostudies-literature

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Superconductivity in (Ba,K)SbO3.

Kim Minu M McNally Graham M GM Kim Hun-Ho HH Oudah Mohamed M Gibbs Alexandra S AS Manuel Pascal P Green Robert J RJ Sutarto Ronny R Takayama Tomohiro T Yaresko Alexander A Wedig Ulrich U Isobe Masahiko M Kremer Reinhard K RK Bonn D A DA Keimer Bernhard B Takagi Hidenori H

Nature materials 20220228 6

(Ba,K)BiO3 constitute an interesting class of superconductors, where the remarkably high superconducting transition temperature Tc of 30 K arises in proximity to charge density wave order. However, the precise mechanism behind these phases remains unclear. Here, enabled by high-pressure synthesis, we report superconductivity in (Ba,K)SbO3 with a positive oxygen-metal charge transfer energy in contrast to (Ba,K)BiO3. The parent compound BaSbO3-δ</s ...[more]

PMID: 35228661

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Project description:Phase relations and solidification behavior in the Ge-rich part of the phase diagram have been determined in two isothermal sections at 700 and 750 °C and in a liquidus projection. A reaction scheme has been derived in the form of a Schulz-Scheil diagram. Phase equilibria are characterized by three ternary compounds: τ(1)-BaRhGe(3) (BaNiSn(3)-type) and two novel phases, τ(2)-Ba(3)Rh(4)Ge(16) and τ(3)-Ba(5)Rh(15)Ge(36-x), both forming in peritectic reactions. The crystal structures of τ(2) and τ(3) have been elucidated from single-crystal X-ray intensity data and were found to crystallize in unique structure types: Ba(3)Rh(4)Ge(16) is tetragonal (I4/mmm, a = 0.65643(2) nm, c = 2.20367(8) nm, and R(F) = 0.0273), whereas atoms in Ba(5)Rh(15)Ge(36-x) (x = 0.25) arrange in a large orthorhombic unit cell (Fddd, a = 0.84570(2) nm, b = 1.4725(2) nm, c = 6.644(3) nm, and R(F) = 0.034). The body-centered-cubic superstructure of binary Ba(8)Ge(43)□(3) was observed to extend at 800 °C to Ba(8)Rh(0.6)Ge(43)□(2.4), while the clathrate type I phase, κ(I)-Ba(8)Rh(x)Ge(46-x-y)□(y), reveals a maximum solubility of x = 1.2 Rh atoms in the structure at a vacancy level of y = 2.0. The cubic lattice parameter increases with increasing Rh content. Clathrate I decomposes eutectoidally at 740 °C: κ(I) ⇔ (Ge) + κ(IX) + τ(2). A very small solubility range is observed at 750 °C for the clathrate IX, κ(IX)-Ba(6)Rh(x)Ge(25-x) (x ∼ 0.16). Density functional theory calculations have been performed to derive the enthalpies of formation and densities of states for various compositions Ba(8)Rh(x)Ge(46-x) (x = 0-6). The physical properties have been investigated for the phases κ(I), τ(1), τ(2), and τ(3), documenting a change from thermoelectric (κ(I)) to superconducting behavior (τ(2)). The electrical resistivity of κ(I)-Ba(8)Rh(1.2)Ge(42.8)□(2.0) increases almost linearly with the temperature from room temperature to 730 K, and the Seebeck coefficient is negative throughout the same temperature range. τ(1)-BaRhGe(3) has a typical metallic electrical resistivity. A superconducting transition at T(C) = 6.5 K was observed for τ(2)-Ba(3)Rh(4)Ge(16), whereas τ(3)-Ba(5)Rh(15)Ge(35.75) showed metallic-like behavior down to 4 K.

Dataset Information

Superconductivity in (Ba,K)SbO₃.

Publications

Superconductivity in (Ba,K)SbO<sub>3</sub>.

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