LaP2: isostructural to MgB2 with charming superconductivity

TL;DR

This paper predicts that LaP2, structurally similar to MgB2, exhibits superconductivity with a Tc of 22.2 K under pressure, highlighting the role of P layers and La electrons in its superconducting properties.

Contribution

It introduces LaP2 as a new pressure-stabilized superconductor with the highest Tc among transition metal phosphides, and elucidates its structural and electronic features.

Findings

LaP2 shows superconductivity with Tc of 22.2 K under pressure.

LaP2's structure is stabilized at pressures as low as 7 GPa.

The superconductivity involves electron-phonon coupling and La electron contributions.

Abstract

The exploration of superconductivity dominated by structural units is of great interest in condense matter physics. MgB2, consisting of graphene-like B, becomes a typical representative of traditional superconductors. Phosphorus demonstrates diverse non-planar motifs through sp3 hybridization in allotropes and phosphides. Here, we report that a pressure-stabilized LaP2, isostructural to MgB2, shows superconductivity with a predicted Tc of 22.2 K, which is the highest among already known transition metal phosphides. Besides electron-phonon coupling of graphene-like P, alike the role of B layer in MgB2, La 5d/4f electrons are also responsible for the superconducting transition. Its dynamically stabilized pressure reaches as low as 7 GPa, a desirable feature of pressure-induced superconductors. The distinct P atomic arrangement is attributed to its sp2 hybridization and out-of-plane symmetric distribution of lone pair electrons. Although P is isoelectronic to N and As, we hereby find the different stable stoichiometries, structures, and electronic properties of La phosphides compared with La nitrides/arsenides at high pressure.