Band Structure of Topological Insulator BiSbTe1.25Se1.75

H Lohani; P Mishra; A Banerjee; K Majhi; R Ganesan; U Manju; D Topwal; P S Anil Kumar; B R Sekhar

doi:10.1038/s41598-017-04985-y

Band Structure of Topological Insulator BiSbTe_1.25Se_1.75

Sci Rep. 2017 Jul 4;7(1):4567. doi: 10.1038/s41598-017-04985-y.

Authors

H Lohani^{1

2}, P Mishra¹, A Banerjee³, K Majhi³, R Ganesan³, U Manju⁴, D Topwal^{1

2}, P S Anil Kumar³, B R Sekhar^{5

6}

Affiliations

¹ Institute of Physics, Sachivalaya Marg, Bhubaneswar, 751005, India.
² Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai, 400085, India.
³ Indian Institute of Science, Bangalore, 560012, India.
⁴ CSIR-Institute of Minerals and Materials Technology, Bhubaneswar, 751005, India.
⁵ Institute of Physics, Sachivalaya Marg, Bhubaneswar, 751005, India. sekhar@iopb.res.in.
⁶ Homi Bhabha National Institute, Training School Complex, Anushakti Nagar, Mumbai, 400085, India. sekhar@iopb.res.in.

Abstract

We present our angle resolved photoelectron spectroscopy (ARPES) and density functional theory results on quaternary topological insulator (TI) BiSbTe_1.25Se_1.75 (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.