Energy-gap opening near the Dirac point after the deposition of cobalt on the (0001) surface of the topological insulator BiSbTeSe$_{2}$

It was shown for the first time that Co subnanometer coaverage, being deposited by molecular beam epitaxy method onto the (0001) surface of the BiSbTeSe$_{2}$ topological insulator at 330$^{\circ}$C, opens an energy band gap in the spectrum of topological surface states in the region of the Dirac point, with a shift in the position of the Dirac point caused by preliminary deposition of the adsorbate at room temperature. The gap band width is 21 $\pm$ 6 meV. Temperature-dependent measurements in the 15–150 K range did not show any width changes.