I4/mcm-Si$_{48}$: An Ideal Topological Nodal-Line Semimetal

TL;DR

This paper identifies and characterizes I4/mcm-Si48 as an ideal silicon-based topological nodal-line semimetal with unique electronic and surface properties, promising for high-speed photoelectric applications.

Contribution

The study discovers a stable silicon allotrope, I4/mcm-Si48, as an ideal topological nodal-line semimetal with detailed symmetry and electronic property analysis.

Findings

I4/mcm-Si48 is thermodynamically stable and dynamically robust.

It hosts a topological nodal-line protected by symmetry.

Exhibits high Fermi velocity Dirac fermions and flat surface states.

Abstract

Topological semimetals (TSMs) have attracted numerous attention due to their exotic physical properties and great application potentials. Silicon-based TMSs are of particularly importance because of their high abundance, nontoxicity and natural compatibility with current semiconductor industry. In this work, an ideal low-energy topological nodal-line semimetal (TNLSM) silicon (I4/mcm-Si$_{48}$) with a clean band crossing at Fermi level is screened from thousands of silicon allotropes by the transferable tight-binding and DFT-HSE calculations. The results of formation energy, phonon dispersion, ab initio molecular dynamics and elastic constants show that I4/mcm-Si48 possesses good stability and is more stable than several synthetized silicon structures. By analyzing the symmetry, it reveals that the topological nodal-line of I4/mcm-Si48 is protected by mirror symmetry and inversion, time-reversal and SU(2) spin-rotation symmetries, and the nearly flat drumhead-like surface spectrum is observed. Furthermore, I4/mcm-Si48 exhibits exotic photoelectric properties and the Dirac fermions with high Fermi velocity (3.4$\sim$4.36$\times$10$^5$ m/s) can be excited by low energy photons. Our study provides a promising topological nodal-line semimetal for fundamental research and potential practical applications in semiconductor-compatible high-speed photoelectric devices.