fig4

Figure 4. Schematics for a few dominant and frequently encountered band structure engineering strategies (clockwise from top): (i) band alignment for increasing the valley degeneracy; (ii) elongated energy surface features; (iii) band inversion followed by spin-orbit-coupling (SOC) for increasing degeneracy and operation close to topological states; (iv) optimal doping; (v) narrow gap materials engineering; (vi) resonant states for Seebeck improvement.