Single Dirac cone on the Cs-covered topological insulator surface Sb2Te3(0001)

Abstract

Using angle-resolved photoelectron spectroscopy we investigate the surface electronic structure of the threedimensional topological insulator (TI) Sb2Te3(0001). Our data show the presence of a topological surface state in the bulk energy gap with the Dirac-point located above the Fermi level. The adsorption of Cs-atoms on Sb2Te3(0001) gives rise to a downward energy shift of the electronic valence band states which saturates at a value of ∼200 meV. For the saturation coverage the Dirac-point of the linearly dispersive surface state resides in close proximity to the Fermi level. The electronic structure of the Cs/Sb2Te3 interface therefore considerably deviates from previously studied metal-TI interfaces based on the isostructural compound Bi2Se3 which points to the importance of atomic composition in these hetero systems.Three-dimensional topological insulators (TIs) are currently generating widespread scientific interest in the condensed matter physics community as the distinct topology of their bulk band structure provokes the existence of robust metallic surface states with unique physical properties.1,2 The surface states locally span the global energy gap in the electronic excitation spectrum of the bulk material and their existence is protected by time-reversal symmetry.3,4 A salient feature of topological surface states (TSSs) lies in their characteristic spin structure introduced by spin-orbit coupling which locks the spin to the direction perpendicular to the wave vector.5 As a consequence of this spin structure the backscattering of the surface state electrons from non-magnetic impurities is strongly suppressed.6 Currently, most research on TIs is devoted to the chalcogenide semiconductors Bi 2 Se 3 7,8 and Bi 2 Te 3 8,9 , related ternary compounds 10,11 as well as to HgTe quantum wells. 12 The TSSs of these materials show a particularly simple dispersion consisting of a single spin-polarized Dirac-cone.The experimental realization of the most appealing properties of TSSs that have been predicted so far will require interface structures between TIs and metal films. This holds for example for the topological magnetoelectric effect at the interface of a TI and a ferromagnet 13,14 as well as for Majorana fermions at the interface of a TI and a superconductor. 15 It is therefore important to investigate the influence of metallic adlayers on the electronic structure of TI surfaces. Surfacesensitive spectroscopic techniques and in particular angleresolved photoelectron spectroscopy (ARPES), which also played a key role in the discovery of TIs 1 , are suitable methods to study modifications in the electronic structure during the formation of interfaces 16 . Indeed, great experimental effort on the basis of ARPES is currently directed towards an improved understanding of the influence of adsorbates on the electronic structure of TI surfaces. [17][18][19][20][21][22][23] However, most of these works have focused on the TI surface Bi 2 Se 3 (0001). It therefore appears essential to expand the present investigati...

Engineering the topological surface states in the(Sb2)m−Sb2Te3(m=0Johannsen1, Autès2, Crepaldi3 et al. 2015Phys. Rev. B201200View full textAdd to dashboardCite

“…Possible applications depend on the ability to control the electronic properties of the TSS. Common strategies for achieving such a control involve chemical substitution and adsorbate doping [9][10][11][12][13]. Alternatively, it has been proposed that multilayer heterostructures could be used to obtain artificial TIs with tunable properties defined by the stacking sequences of the constituent two-dimensional building blocks [14][15][16].…”

Bulk and surface electron dynamics in ap-type topological insulatorSnSb2Te4

“…However, intrinsic p doping of antimony-containing materials does not permit to access the Dirac point by conventional angle-resolved photoelectron spectroscopy [12] even after doping by alkali-metal atoms [13]. Angle-resolved two-photon photoemission (2PPE) uses a pump-probe process to access the unoccupied electronic states as indicated by the arrows in Fig.…”

Breaking time-reversal symmetry at the topological insulator surface by metal-organic coordination networks

“…The consequences of an incommensurate growth of MOCN/TI are also discussed. We believe that the results obtained reflect general characteristic features of the TCNE-, TCNB-, and TCNQ-based MOCNs deposited on top of tetradymite-type TIs [8,[72][73][74]. The main conclusion of this study is that the time-reversal symmetry can indeed be broken by the deposition of a MOCN on top of the TI surface.…”

“…5). Although the Fermi level position can be tuned into the bulk band gap by electrical gating, the use of p-doped TIs (e.g., Sb 2 Te 3 [72]) as substrates for MOCNs deposition can help in decreasing the magnitude of the gate bias voltage required to access the Dirac state and the induced DP gap in particular.…”