Ideal inner nodal chain semimetals in Li2XY (X = Ca, Ba; Y = Si, Ge) materials

TL;DR

Li2XY compounds are identified as ideal, stable inner nodal chain semimetals with distinctive band structures and surface states, providing promising platforms for experimental observation and potential applications of nodal chain fermions.

Contribution

This work predicts and characterizes Li2XY compounds as the first known ideal inner nodal chain semimetals with clear experimental signatures.

Findings

Presence of two connecting nodal loops with hybrid or type-I dispersion

Pronounced nontrivial surface states indicating nodal chain features

Materials are ambient-stable and suitable for experimental detection

Abstract

The chain-type nodal loops in the reciprocal space can generate exotic nodal chain fermions. Here, we report that Li2XY (X = Ca, Ba; Y = Si, Ge) compounds are ideal inner nodal chain semimetals. Their band structures are composed of two connecting nodal loops with either hybrid or type-I band dispersion. The signatures of the nodal chain, such as the nontrivial surface states, are quite pronounced in these Li2XY compounds since there is only a single inner nodal chain without other extraneous bands near the Fermi level. These compounds are existing materials and ambient-stable, which is available to realize the experimental detection of inner nodal chain fermions or further the practical applications.