Electride and superconductivity behaviors in Mn5Si3-type intermetallics

Abstract

Electrides are unique in the sense that they contain localized anionic electrons in the interstitial regions. Yet they exist with a diversity of chemical compositions, especially under extreme conditions, implying generalized underlying principles for their existence. What is rarely observed is the combination of electride state and superconductivity within the same material, but such behavior would open up a new category of superconductors. Here, we report a hexagonal Nb 5 Ir 3 phase of Mn 5 Si 3 -type structure that falls into this category and extends the electride concept into intermetallics. The confined electrons in the one-dimensional cavities are reflected by the characteristic channel bands in the electronic structure. Filling these free spaces with foreign oxygen atoms serves to engineer the band topology and increase the superconducting transition temperature to 10.5 K in Nb 5 Ir 3 O. Specific heat analysis indicates the appearance of low-lying phonons and two-gap s-wave superconductivity. Strong electron-phonon coupling is revealed to be the pairing glue with an anomalously large ratio between the superconducting gap Δ 0 and T c , 2Δ 0 /k B T c = 6.12. The general rule governing the formation of electrides concerns the structural stability against the cation filling/extraction in the channel site.

Crossover from multiple- to single-gap superconductivity in Nb5Ir3−xPtxO alloys

“…Nb 5 Ir 3 exhibits an unusual interplay of electride and SC states, whereas only SC remains in Nb 5 Ir 3 O 1 . Density functional theory (DFT) calculations indicate Nb 5 Ir 3 to be a multiband metal, whose density of states (DOS) at the Fermi level is dominated by the Nb 4d-and Ir 5d-orbitals 1 . The increase of T c in Nb 5 Ir 3 O x is most likely attributed to the enhanced electron-phonon coupling strength or to an increased DOS at the Fermi level (with extra Nb-4d and O-2p contributions) 1 .…”

“…Density functional theory (DFT) calculations indicate Nb 5 Ir 3 to be a multiband metal, whose density of states (DOS) at the Fermi level is dominated by the Nb 4d-and Ir 5d-orbitals 1 . The increase of T c in Nb 5 Ir 3 O x is most likely attributed to the enhanced electron-phonon coupling strength or to an increased DOS at the Fermi level (with extra Nb-4d and O-2p contributions) 1 . On the other hand, by applying external pressure, T c decreases monotonically from 10.5 K at ambient pressure to 9.5 K at 13 GPa 1,6 .…”

Discovery of Hidden Classes of Layered Electrides by Extensive High-Throughput Material Screening

“…Despite many endeavors since the first crystalline electride grown three decades ago, 3 only a few electrides have been synthesized. [4][5][6][7][8][9][10][11][12][13] The first room-temperature stable inorganic electride was reported in 2003 by removing oxygen ions from the crystallographic cages of 12CaO.7Al 2 O 3 , yielding [Ca 24 Al 28 O 64 ] 4+ (4e -). 5 The high density of anionic electrons with loosely bounded nature makes [Ca 24 Al 28 O 64 ] 4+ (4e -) promising for a plethora of applications, such as efficient thermionic emitters, 14 electroninjection electrode for organic light-emitting diodes, 15,16 and high performance catalysts.…”

Identifying quasi-2D and 1D electrides in yttrium and scandium chlorides via geometrical identification

“…[24][25][26][27] Besides, many electrides (e.g., Li, 28 Na, 29 Mg, 30 C 31 , Na 2 He, 32 and Sr 5 P 3 33 ) have been found to reveal a generalized structure under pressure. 34 Depending on the dimensionality of the anionic electrons localizations, electrides can be classified into 0D, 1D, and 2D systems, 13,20,35,36 where the anionic electrons are either isolated or bonded with each other in the cage-like, channel-like, or layer-like voids. These interesting results suggest a geometrical way to obtain the diverse 'interstitial spaces' in a lattice that can stabilize excess electrons, which can provide a vast configuration space for computational discovery.…”