Electronic band structure for occupied and unoccupied states of the natural topological superlattice phase Sb2Te

Abstract

We present an experimental study describing the effects of surface termination on the electronic structure of the natural topological superlattice phase Sb2Te. Using scanning angle-resolved photoemission microscopy, we consistently find various non-equivalent regions on the same surface after cleaving various Sb2Te single crystals. We were able to identify three distinct terminations characterized by different Sb/Te surface stoichiometric ratios and with clear differences in their band structure. For the dominating Te-rich termination, we also provide a direct observation of the excited electronic states and of their relaxation dynamics by means of time-resolved angle-resolved photoemission spectroscopy. Our results clearly indicate that the surface electronic structure is strongly affected by the bulk properties of the superlattice.

Ultrafast Electron Dynamics in Topological Materials

“…These results were immediately confirmed and further investigated in other studies on Bi 2 Se 3 ; other compounds of the same family were later studied with the same approach, like for instance Sb 2 Te 3 , SnSb 2 Te 4 , where a much faster (sub‐ps) dynamics was instead observed. The continuous discovery of surface topological properties in new classes of materials will contribute to providing a more extensive data set for their ultrafast dynamics properties, as recently demonstrated for novel materials like Zr 2 Te 5 , the superlattice series (Sb 2 ) m ‐Sb 2 Te 3 or Kondo topological insulators like SmB 6 …”

Polymorphism in Post-Dichalcogenide Two-Dimensional Materials

“…The nature of the interlayer bonding between the blocks differs for Sb and Bi compounds. In the case of antimony tellurides, all three gaps are vdW in nature, ,, and the Sb 2 Te 3 –Sb 2 Te 3 , Sb 2 –Sb 2 , and Sb 2 Te 3 –Sb 2 interlayer distances are 2.7 Å, 2.2–2.3 Å, and 2.4–2.5 Å, respectively. For comparison, the Sb 2 Te 3 –Sb 2 Te 3 interlayer distance is 2.8 Å in the α-Sb 2 Te 3 structure .…”

“…Similar to the M V 2 X 3 compounds, members of the (M V 2 ) m (M V 2 X 3 ) n series show topologically nontrivial properties and are thermoelectrics. ,,− Different surface terminations and termination-dependent electronic properties have been identified for cleaved Sb 2 Te and Bi 4 Se 3 crystals by ARPES studies where a complex interplay between structure and surface electronic properties was discovered. BiTe was recently discovered to be a dual 3D topological insulator (weak topological insulator and topological crystalline insulator phases simultaneously) and also showed termination-dependent surface states. , These findings suggest ample opportunity for further study of the members of (M V 2 ) m (M V 2 X 3 ) n series in the 2D limit.…”

Bulk defects and surface state dynamics in topological insulators: The effects of electron beam irradiation on the ultrafast relaxation of Dirac fermions in Bi2Te3

“…Several attempts to decrease the significant bulk carrier contribution were based on chemical doping [15,16], increasing the surface-to-bulk ratio using nanostructur-ing which can be performed through mechanical exfoliation or growth of TI nanowires and nanoribbons [17,18], epitaxial growth of TI/II-VI semiconductor superlattices [19,20], and irradiation by high-energy electron beams: in particular, intrinsic quantum transport measurements and angle-resolved photoemission spectroscopy (ARPES) revealed that a technique based on irradiation with swift (∼ 2.5 MeV energy) electron beams at specific electron doses [21] doesn't affect the Dirac energy dispersionimmmune to disorder-and offers a path to large scale transport in topological SSs. Furthermore, this experimental study has indicated that it is possible, by following a thermal protocol, to tune the band position from the irradiation-induced n-type back towards the charge neutrality point where the system remains for months.…”