Electronic structure of ultrathin Cs/Bi$_2$Se$_3$ interfaces

G. V. Benemanskaya^a, S. N. Timoshnev<sup>b

a</sup> Ioffe Institute, St. Petersburg, Russia
^b Alferov Federal State Budgetary Institution of Higher Education and Science Saint Petersburg National Research Academic University of the Russian Academy of Sciences, St. Petersburg, Russia

Abstract: The electronic structure of ultrathin Cs/Bi$_2$Se$_3$ interfaces has been studied by photoelectron spectroscopy using synchrotron radiation. The experiments were carried out in situ in ultrahigh vacuum with submonolayer Cs coverages on Bi$_2$Se$_3$ samples. It was found that the adsorption of Cs causes changes in the core level spectra of Bi $4f$, Bi $5d$, Se $3d$. It has been established that Cs atoms are adsorbed predominantly on Bi atoms in the upper surface layer. The states of the valence band were studied for a clean Bi$_2$Se$_3$ surface and for the Cs/Bi$_2$Se$_3$ interface. Near the Fermi level, 2D topological states have been found. Two induced surface states appear in the region of the valence band upon adsorption of Cs.

Keywords: topological insulators, electronic structure, ultrathin interfaces, photoelectron spectroscopy.

Received: 27.04.2022
Revised: 24.10.2022
Accepted: 25.10.2022

DOI: 10.21883/PJTF.2022.24.54020.19236

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