Topological phase engineering of rutile GeO2 with strain

Nodal-line semimetals serve as the parent phase for various topological states. By manipulating spin-orbit coupling (SOC), time-reversal symmetry, or spatial inversion symmetry, a Dirac nodal-line semimetal can transition into a 3D Dirac semimetal, Weyl semimetal, or topological insulator.

In this study, we present the topological phase engineering of rutile GeO₂ under strain through first-principles calculations. Without considering SOC effect, applying tensile strain to GeO₂ induces a transformation from a trivial insulator to a Dirac nodal-line semimetal, characterized by two orthogonal and interconnected Dirac nodal rings protected by mirror symmetry. When SOC is taken into account, the band degeneracy persists only at two points, resulting in a 3D Dirac semimetal. Nonetheless, due to the negligible strength of SOC in GeO₂, its nodal-line semimetal properties remain largely intact even after including SOC effects.

Our findings provide valuable insights for the topological phase engineering and potential spintronics applications of GeO₂.