Nodal-chain network, intersecting nodal rings and triple points coexisting in nonsymmorphic Ba3Si4

TL;DR

This paper reports the discovery of a topological metal Ba3Si4 that hosts multiple coexisting topological features such as nodal-chain networks, intersecting nodal rings, and triple points, all without spin-orbit coupling.

Contribution

It reveals a 'clean' topological metal with diverse topological elements generated by band crossings, and demonstrates how external strain can induce phase transitions to new topological phases.

Findings

Ba3Si4 hosts coexisting topological features including nodal-chain network, intersecting nodal rings, and triple points.

The topological elements are generated by crossings of three energy bands, showing their correlated nature.

External strain induces phase transitions to phases with Hopf links, nodal chains, and new intersecting nodal rings.

Abstract

Coexistence of topological elements in a topological metal/semimetal (TM) has gradually attracted attentions. However, the non-topological factors always mess up the Fermi surface and cover interesting topological properties. Here, we find that Ba3Si4 is a "clean" TM in which coexists nodal-chain network, intersecting nodal rings (INRs) and triple points, in the absence of spin-orbit coupling (SOC). Moreover, the nodal rings in the topological phase exhibit diverse types: from type-I, type-II to type-III rings according to band dispersions. All the topological elements are generated by crossings of three energy bands, and thus they are correlated rather than mutual independence. When some structural symmetries are eliminated by an external strain, the topological phase evolves into another phase including Hopf link, one-dimensional nodal chain and new INRs.