Pristine and strained anisotropic group velocity and effective mass of surface Dirac fermions in the topological crystalline insulator SnTe

Abstract

Abstract An analysis of the strain-induced group velocity(GV) and effective mass(EM) of massless topological Dirac fermions on the SnTe(001) surface, protected by crystalline symmetry, is presented. Using the traditional semi-classical k → ⋅ p → approach by associating fermions with wave-packets, we find that the expression for the energy dispersion surface as well as both GV and EM are anisotropic in the absence and presence of strain. The band structure calculations indicate that the massive Dirac fermions emerge for strained SnTe(001) surface. However, under strong strains, GVs and EMs of all branches of conduction and valence bands are the same quantitatively, but still anisotropic along different directions. On the other hand, depending on the special critical compressive and/or tensile strains, the direction of the fermionic waves is reversed. Further, the behavior of heavy and light masses are characterized qualitatively with strain modulus and direction. Our results are favorable for the thermoelectric properties of SnTe semiconductor since electronic features are coupled to the heat transports.