Observation of Dirac-like surface state bands on the top surface of BiSe

¹ Physics Department, Technion-Israel Institute of Technology - Haifa 32000, Israel
² Department of Physics, Indian Institute of Science - Bangalore 560012, India
³ Elettra Sincrotrone Trieste - Strada Statale 14 km 163.5, 34149, Trieste, Italy
⁴ Institute of Physics, Sachivalaya Marg - Bhubaneswar 751005, India

^(a) sekhar@iopb.res.in (corresponding author)

Received: 3 December 2020
Accepted: 9 March 2021

Abstract

Weak topological insulators (TIs) host non-trivial topological surface state bands (SSBs) at the side surface of the crystal while the top (001) surface can be topologically either dark or light. In our detailed angle-resolved photoelectron spectroscopy (ARPES) study we found Dirac-like linearly dispersive SSBs on the (001) surface of BiSe and Sb-doped (8%) BiSe. The lower part of the SSBs buries deep in the bulk valence band (BVB) and the overlap region between the SSBs and BVB increases significantly with Sb doping. These results highlight the role of the interlayer coupling between the Bi bilayer and the Bi₂Se₃ quintuple layer (QL). Furthermore, in the overlap region the SSBs deviate from the Dirac-like linear dispersion. Interestingly, we observed a large intensity imbalance ) in the SSBs located at the positive and negative directions. This asymmetry pattern ) gradually reverses to ) as the excitation energy scans from low (14 eV) to high (34 eV) values. The observed photon energy-dependent intensity variation could be a signature of the mixing between the spin and the orbit texture of the SSBs.