Natural sulfur-containing minerals as topological insulators with a wide band gap

Abstract

The electronic structure of quaternary natural minerals PbBi 2 Te 2 S 2 (aleksite), Pb 2 Bi 2 Te 2 S 3 (saddlebackite), and PbBi 4 Te 4 S 3 ( C phase) has been theoretically studied. These compounds have a layered structure: aleksite and saddlebackite are formed by seven- and nine-layer blocks, respectively, and C phase consists of five- and seven-layer blocks separated by van der Waals gaps. It has been shown that all studied materials are three-dimensional topological insulators with a wide band gap in the electronic spectrum and have a high spin polarization. For these reasons, they are promising for applications.