Ab initio prediction of nontrivial topological band and superconductivity in stable metallic Si allotropes at ambient pressure

Abstract

Based on first-principles density functional calculations, we report the existence of both nontrivial band topology and superconductivity in three metallic Si allotropes, termed Cmcm−Si4, Cmmm−Si4, and I4/mmm−Si4. Cmcm−Si4 and I4/mmm−Si4 are predicted in this study, whereas Cmmm−Si4 was proposed in previous theoretical calculations. These metastable allotropes retain their crystalline structure at ambient pressure and exhibit superconductivity at the critical temperatures of 1.2–11.4 K. We investigate the topological characteristics of the electronic states and find the weak topological nature for all three allotropes. For Cmcm−Si4, in particular, the formation of the surface Dirac point is clearly identified. Our result provides a promising platform for realizing a topological superconducting state in all-Si systems at ambient pressure.

Source-reported materials — not catalogue approval

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