Prediction and control of the topological phases in Cs(Na, K)₂Bi compound using strain-engineering

Design and discovery of topological quantum materials with exotic physical properties are some of the most challenging but fertile fields with revolutionary technological impacts. Topological materials such as Dirac semimetals, Weyl semimetals, and Nodal line semimetals have attracted much attention because of their unique electronic properties. However, if such materials are to underlay a technology, it is crucial to be able to control their topological phases systematically. A practical approach to control the topological phase conversion is based on strain engineering, where the symmetry and the electronic band structure can be controlled using an external stimulus. In the present work, we predict the highly stable new bialkali bismuthides compound Cs(Na,K)₂Bi, that can take a diverse set of topological phases by strain-engineering. Based on first-principles studies, our findings reveal that the hydrostatic lattice compression, uniaxial compression, and uniaxial tension can transition Cs(Na,K)₂Bi to a trivial semiconductor, a topological insulator, a normal insulator, a Weyl semimetal, a Dirac semimetal, and a Nodal Line semimetal.