Abstract
Topological crystalline insulators form a class of semiconductors for which surface electron states with the Dirac dispersion relation are formed on surfaces with a certain crystallographic orientation. Pb1−xSnxTe alloys belong to the topological crystalline phase when the SnTe content x exceeds 0.35, while they are in the trivial phase at x < 0.35. For the surface crystallographic orientation (111), the appearance of topologically nontrivial surface states is expected. We studied the photoelectromagnetic (PEM) effect induced by laser terahertz radiation in Pb1−xSnxTe films in the composition range x = (0.11–0.44), with the (111) surface crystallographic orientation. It was found that in the trivial phase, the amplitude of the PEM effect is determined by the power of the incident radiation, while in the topological phase, the amplitude is proportional to the flux of laser radiation quanta. A possible mechanism responsible for the effect observed presumes damping of the thermalization rate of photoexcited electrons in the topological phase and, consequently, prevailing of electron diffusion, compared with energy relaxation.
Highlights
The physics of topological insulators is one of the rapidly developing areas of modern solid-state physics
In addition to topological insulators for which the existence of surface states is due to the time-reversal symmetry, there is another class of topologically nontrivial materials—
It has been demonstrated that the PEM effect amplitude scales up as the incident terahertz radiation power for the trivial phase of Pb1−x Snx Te films, whereas it is proportional to the incident photon flux for the topological phase samples
Summary
The physics of topological insulators is one of the rapidly developing areas of modern solid-state physics. In these materials, the energy positions of the conduction and valence bands in the bulk are inverted because of the strong spin–orbit interaction. In addition to topological insulators for which the existence of surface states is due to the time-reversal symmetry, there is another class of topologically nontrivial materials—. Topological crystalline insulators—for which the appearance of topological surface states is due to the symmetry of the crystal lattice [4,5,6,7]. Nanomaterials 2021, 11, 3207 surface states arise at all surfaces of the material, while in topological crystalline insulators, they form only at surfaces with a certain crystallographic orientation.
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