Band Structure of Topological Insulator BiSbTe1.25Se1.75

Abstract

We present our angle resolved photoelectron spectroscopy (ARPES) and density functional theory results on quaternary topological insulator (TI) BiSbTe1.25Se1.75 (BSTS) confirming the non-trivial topology of the surface state bands (SSBs) in this compound. We find that the SSBs, which are are sensitive to the atomic composition of the terminating surface have a partial 3D character. Our detailed study of the band bending (BB) effects shows that in BSTS the Dirac point (DP) shifts by more than two times compared to that in Bi2Se3 to reach the saturation. The stronger BB in BSTS could be due to the difference in screening of the surface charges. From momentum density curves (MDCs) of the ARPES data we obtained an energy dispersion relation showing the warping strength of the Fermi surface in BSTS to be intermediate between those found in Bi2Se3 and Bi2Te3 and also to be tunable by controlling the ratio of chalcogen/pnictogen atoms. Our experiments also reveal that the nature of the BB effects are highly sensitive to the exposure of the fresh surface to various gas species. These findings have important implications in the tuning of DP in TIs for technological applications.

Spatially varying electronic dephasing in three-dimensional topological insulators

“…In compensated semiconductors, the donor dopant density(N d ) is close to the acceptor dopant density(N a ), but cannot be made to be exactly equal. This naturally leads to a transition of dopant DOS N µ across the mid-gap energy level(E mg ), which roughly(though not exactly) corresponds to the Dirac point in our material as verified by ARPES measurements [24]. Since R hop ∝ N −1/3 µ , L φ in the n-type region differs from that in the p-type region, but otherwise remains constant with the gate voltage.…”

“…We choose the bulk insulating topological insulator BiSbTe 1.25 Se 1.75 for our studies. Details of single crystal preparation and ARPES measurements are provided elsewhere [23,24].…”

Signatures of Topological Superconductivity in Bulk-Insulating Topological Insulator BiSbTe1.25Se1.75 in Proximity with Superconducting NbSe2

“…In our experiments, the bulk bands originate from J = 1/2 Se(Te) p-type atomic orbitals, which form the valence band of our system with an experimentally measured band-width of ∆ V B 200 meV 49 (see supplementary material section G). This results in a sub-band spacing ∆ SB = ∆ V B /N z 4meV for a 50 QL layer slab.…”

Quantized transport in topological insulator n-p-n junctions

“…Our devices are fabricated from exfoliated thin flakes of the topological insulator BiSbTe 1.25 Se 1.75 (BSTS), belonging to the class of highly bulk insulating TIs [23][24][25][26]. Previous angle-resolved photoemission spectroscopy (ARPES) studies [27] and transport experiments [28] by us show that the chemical potential in this material lies within the bulk band gap, and the bulk conduction is undetectable below 100K. A thin layer of hexagonal Boron-Nitride (h-BN) covering the BSTS flake serves as the top gate dielectric while the Si/SiO 2 substrate forms the back gate (Fig.…”