Fig. 1: Evolution of band structures due to different compressive strains.

The left plots show the ab initio electron band structures of GeTe (red), SnTe (blue), and PbTe (green). The solid and dashed lines represent the crystal with and without a 3% compressive strain, respectively. The right plot schematically illustrates the transition of the band structure of SnTe after compression. The bottoms of the two new-formed conduction valleys in SnTe are denoted as Q (located at 0.4831b₁ + 0.5169b₂ + 0.5000b₃ in the direction from the L to W point) and Λ (located at 0.4575b₁ + 0.4575b₂ + 0.4575b₃ in the direction from the L to Г point), where b is the reciprocal lattice vector.