Double Fe-impurity charge state in the topological insulator Bi2Se3

Abstract

The influence of individual impurities of Fe on the electronic properties of topological insulator Bi 2 Se 3 is studied by Scanning Tunneling Microscopy. The microscope tip is used in order to remotely charge/discharge Fe impurities. The charging process is shown to depend on the impurity location in the crystallographic unit cell, on the presence of other Fe impurities in the close vicinity, as well as on the overall doping level of the crystal. We present a qualitative explanation of the observed phenomena in terms of tip-induced local band bending. Our observations evidence that the specific impurity neighborhood and the position of the Fermi energy with respect to the Dirac point and bulk bands have both to be taken into account when considering the electron scattering on the disorder in topological insulators. arXiv:1712.00915v2 [cond-mat.mes-hall]

Josephson current mediated by ballistic topological states in Bi2Te2.3Se0.7 single nanocrystals

“…The main disadvantage of the exfoliation method is the uncontrolled shape, thickness, lateral size, and orientation of the resulted flakes. Moreover, numerous atomic defects and surface quintuple steps already existing in the pristine crystal or created during the exfoliation process 6,24,37 modify the electron transport properties of the devices 38 .…”

Tunable high speed atomic rotor in Bi$_{2}$Se$_{3}$ revealed by current noise

“…The shift of its resonance with respect to conventional Fe impurities (see Fig. 1b) can be expected for such a modified environment 21 .…”

“…Figure 1a shows a constant current image of the selenium top-layer of the Bi 2 Se 3 which is bulk-doped with 0.2% Fe. The Fe impurities preferentially replace sub-surface bismuth atoms 18,19 and can be identified by the shape and voltage dependence of their localised energy levels 20,21 . Additionally, due to the smaller Fe-Se bond length 19 , replacement of a Bi atom by an Fe impurity in the first layer below the surface leads to a reduced height of the three neighbouring Se atoms, seen as dark triangles in topography at voltages near the chemical potential, F .…”

Tunable High Speed Atomic Rotor in Bi2Se3 Revealed by Current Noise

“…The shift of its resonance with respect to conventional Fe impurities (see Figure 1b) can be expected for such a modified environment. 21 We speculate that for the offcenter Fe impurity, the surface Se atom farthest from the Fe impurity drops below the Se plane, whereas the two Se atoms closer to the Fe impurity will be lifted above the Se plane. three orientations in this scenario then correspond to the three equivalent positions of the off-center Fe impurity, where the current into the Fe provides the energy required to hop from one position to another.…”

“…Figure a shows a constant current image of the selenium top-layer of 0.2% Fe-doped Bi 2 Se 3 . The Fe impurities preferentially replace subsurface bismuth atoms , and can be identified by the shape and voltage dependence of their localized energy levels. , Additionally, due to the smaller Fe–Se bond length, replacement of a Bi atom by an Fe impurity in the first layer below the surface leads to a reduced height of the three neighboring Se atoms, seen as dark triangles in topography at voltages near the chemical potential, ϵ F . Importantly, all resonant levels and topographic features normally maintain the triangular symmetry of the lattice.…”