Efficient Topological Materials Discovery using Symmetry Indicators

February 19, 2019
pie chart of topological materials statistics

Fig. 6: Statistics of topological materials (see below).

Although the richness of spatial symmetries has led to a rapidly expanding inventory of possible topological crystalline (TC) phases of electrons, physical realizations have been slow to materialize due to the practical difficulty in ascertaining band topology in realistic calculations. A new article in Nature Physics, Researchers at Nanjing University in China, led by Xiangang Wan, and the Harvard team, led by Ashvin Vishwanath, integrate the recently established theory of symmetry indicators of band topology into first-principles band-structure calculations, and test it on a database of previously synthesized crystals. On applying their algorithm to just 8 out of the 230 space groups, teh scientists are able to efficiently unearth topological materials and predict a diversity of topological phenomena, including: a screw-protected three-dimensional TC insulator, β-MoTe2, with gapped surfaces except for one-dimensional helical hinge states; a rotation-protected TC insulator, BiBr, with coexisting surface Dirac cones and hinge states; non-centrosymmetric Z2 topological insulators undetectable using the well-established parity criterion, AgXO (X = Na, K, Rb); a Dirac semimetal MgBi2O6; a Dirac nodal-line semimetal AgF2; and a metal with three-fold degenerate band crossing near the Fermi energy, AuLiMgSn. This work showcases how recent theoretical insights into the fundamentals of band structures can aid in the practical goal of discovering new topological materials.

Read Feng Tang, Hoi Chun Po, Ashvin Vishwanath & Xiangang Wan, "Efficient topological materials discovery using symmetry indicators," Nature Physics (2019) https://doi.org/10.1038/s41567-019-0418-7.

Also read "Symmetry indicators unearth new topological materials" by Belle Dumé in Physics World, 16 Feb 2019. https://physicsworld.com/a/symmetry-indicators-unearth-new-topological-materials/.