Effect of surface defects and few-atomic steps on the local density of states of the atomically-clean surface of Bi2Se3 topological insulator

Abstract

The results of ultra-high vacuum low-temperature scanning-tunneling microscopy (STM) and spectroscopy (STS) of atomically clean (111) surface of the topological insulator Bi2Se3 are presented. We observed several types of new subsurface defects whose location and charge correspond to p-type conduction of grown crystals. The sign of the thermoelectric effect also indicates p-type conduction. STM and STS measurements demonstrate that the chemical potential is always located inside the bulk band gap. We also observed changes in the local density of states in the vicinity of the quintuple layer steps at the studied surface. This changes correspond either to the shift of the Dirac cone position or to the shift of the chemical potential near the step edge.

Disorder enabled band structure engineering of a topological insulator surface

“…Defect resonance states have been observed by STM less than 200 meV above the surface Dirac point, surrounding point defects 14 15 and at step edges between plateaus differing in height by one quintuple layer 18 19 . Characteristic local density of states (LDOS) distributions measured by STM at the defect lattice sites are plotted as black curves in Fig.…”

“…Altogether with the intuition that topological properties of band structure should be inherently impervious to weak perturbations, this led to a pervasive characterization that topological interfaces are essentially blind to the presence of non-magnetic defects. It is only with the recent advent of more detailed non-perturbative numerical investigations and targeted scanning tunnelling microscopy (STM) experiments 12 13 14 15 16 17 18 19 20 21 22 23 24 25 that elements of this picture have been overturned. It is now known that, rather than being blind to defects, topological Dirac cone electrons actually bind loosely to atomic point defects in energy levels that fall very close to the Dirac point (see states labelled ‘resonance' in Fig.…”

Connection topology of step edge state bands at the surface of a three dimensional topological insulator

“…Three dimensional topological insulators (TI) are materials with Z 2 topological order that manifest conducting two-dimensional (2D) Dirac cone surface states protected by time-reversal symmetry [1,2]. The surface state electrons resist scattering from weak non-magnetic perturbations [1][2][3][4][5][6][7][8][9], however recent studies have shown that strongly perturbing point-and step-like surface defects can introduce new in-gap states and modify the band structure near the Dirac point [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. Here, we present a numerical and analytic analysis of the singlequintuple layer step defect of Bi 2 Se 3 -family TIs, to explore the nature of the associated edge state.…”

Toward the Intrinsic Limit of the Topological InsulatorBi2Se3

“…One of the major material hurdles of TI research is the lack of clear identification and understanding of native defects, which is necessary for optimization of synthesis and device fabrication to achieve desired sample quality. A recent work reported p-type Bi 2 Se 3 single crystals without doping, yet the mechanism of p-type conduction and associated native defects were not identified [21].…”