Increasing the number of topological nodal lines in semimetals via uniaxial pressure

TL;DR

This study demonstrates that applying uniaxial pressure to BaSn2 semimetals induces a topological phase transition, increasing the number of topological nodal lines, which could be experimentally verified through magnetic field responses.

Contribution

It reveals how uniaxial pressure causes a topological-to-topological phase transition in BaSn2, increasing the nodal lines, based on density functional theory and tight-binding models.

Findings

Emergence of a second nodal line above 4 GPa pressure

Both phases retain nontrivial topological character

Orbital overlaps and symmetry preservation drive the transition

Abstract

The application of pressure has been demonstrated to induce intriguing phase transitions in topological nodal-line semimetals. In this work we analyze how uniaxial pressure affects the topological character of BaSn2 , a Dirac nodal-line semimetal in the absence of spin-orbit coupling. Using calculations based on the density functional theory and a model tight-binding Hamiltonian, we find the emergence of a second nodal line for pressures higher than 4 GPa. We examine the topological features of both phases demonstrating that a nontrivial character is present in both of them. Thus, providing evidence of a topological-to-topological phase transition in which the number of topological nodal lines increases. The orbital overlap increase between Ba dxz and dyz orbitals and Sn pz orbitals and the preservation of crystal symmetries are found to be responsible for the advent of this transition. Furthermore, we pave the way to experimentally test this kind of transition by obtaining a topological relation between the zero-energy modes that arise in each phase when a magnetic field is applied.