Strain-induced quantum topological phase transitions in Na3Bi

Abstract

Strain can be used as an effective tool to tune the crystal structure of materials and hence to modify their electronic structures, including topological properties. Here, taking Na3Bi as a paradigmatic example, we demonstrated with first-principles calculations and k · p models that the topological phase transitions can be induced by various types of strains. For instance, the Dirac semimetal phase of ambient Na3Bi can be tuned into a topological insulator (TI) phase by uniaxial strain along the 100 axis. Hydrostatic pressure can let the ambient structure transfer into a new thermodynamically stable phase with Fm3m symmetry, coming with a perfect parabolic semimetal having a single contact point between the conduction and valence bands, exactly at Γ point on the Fermi level like α-Sn. Furthermore, uniaxial strain in the 100 direction can tune the new parabolic semimetal phase into a Dirac semimetal, while shear strains in both the 100 and 111 directions can take the new parabolic semimetal phase into a TI. k · p models are constructed to gain more insights into these quantum topological phase transitions. At last, we calculated surface states of Fm3m Na3Bi without and with strains to verify these topological transitions.

Dimensional Crossover and Topological Phase Transition in Dirac Semimetal Na3Bi Films

“…Furthermore, the mini gap may also be influenced by other factors such as the effect of tunneling background, doping, disorder, strain, etc. 14,24,[39][40][41] Scrutiny over the spectra of thin films from 5-8…”

Predicting Dirac semimetals based on sodium ternary compounds

“…28 In fact, even now the ground state of Na 3 Bi is still under debate. 29,30 Electronic structures The calculated electronic structures of all three materials using the Perdew-Burke-Ernzerhof (PBE) functional and the Heyd-Scuseria-Ernzerhof (HSE) hybrid-functional are shown in the top and middle panels of Fig. 3, respectively.…”

From Multiple Nodal Chain to Dirac/Weyl Semimetal and Topological Insulator in Ternary Hexagonal Materials

“…28,29 If external strain was introduced, the Dirac point could be gaped and the DSM would be tranformed into a topological insulator. [30][31][32] The above analysis is well known for decades, but the transformation process is rarely observed in real materials.…”