Topological states of Sb thin films contacted by a single sheet of heterogeneous atoms

Abstract

We found that thin antimony films contacted by a single layer of a variety of atoms can form topological surface and interface states in the gap of bulk energy bands that preserve time-reversal symmetry. Using density functional calculation, we have included bismuth, graphene, boron-nitride and boron-doped graphene layers in our investigation. In most cases, Dirac cones are found in the band structures and spin textures indicate no back scattering of conduction electrons. In the case of a BC 3 layer deposited on an Sb film as thin as three bilayers, a Dirac cone consisting mostly of interface states is formed close to the Fermi level. If the composite is gated by an adjustable voltage, electron transport can switch between two modes of opposite spins, and between one or two modes of 100% spin polarization. The results should be very useful in the applications of topological conduction and spintronics.

Realization of Dirac Cones in Few Bilayer Sb(111) Films by Surface Modification

“…The TIs discovered so far include simple semimetals (Sb and Bi) [ 4 , 21 – 29 ], alloys (Bi 1 − x Sb x ) [ 4 , 16 ], binary compounds (HgTe, Bi 2 Se 3 , Sb 2 Te 3 , and Bi 2 Te 3 ) [ 4 – 10 , 20 , 30 – 36 ], and ternary semiconducting Heusler compounds [ 12 – 14 ]. As a simple elemental TI, semimetal Sb has the same nontrivial topological order as Bi 1 − x Sb x for x > 0.07 [ 4 , 21 ].…”

“…As a simple elemental TI, semimetal Sb has the same nontrivial topological order as Bi 1 − x Sb x for x > 0.07 [ 4 , 21 ]. Two Rashba-type spin-split surface bands on Sb(111), connected to the bulk conduction and the valence bands separately, result in a single Dirac cone within the bulk bandgap of Sb [ 21 – 29 ]. Importantly, Sb(111) thin films with a thickness of ≤15 bilayers (BL; with 1 BL = 3.75 Å) can be converted into a 3D TI due to the quantum confinement effect which opens up a positive bandgap for the bulk states [ 24 – 26 ].…”

Thin films of topological crystalline insulator SnTe in contact with heterogeneous atomic layers

“…Although surface band gaps can be closed and Dirac cones formed for thick SnTe films, thinner films are more readily synthesized and more flexible for integration into nano-scale two-dimensional devices. The problem of quantum tunneling between the two surfaces of thinner films due to their stronger coupling can be overcome by impurity doping in one of the surface layer or by placing the film in contact with a heterogeneous atomic layer or substrate [21][22][23], thus removing the degeneracy of the two surfaces. The surface interacting with impurity atoms or heterogeneous layers tends to shift its energy levels away from those of the pristine surface, and in turn makes tunneling more difficult.…”

Realization of Dirac Cones in Few Bilayer Sb(111) Films by Surface Modification

“…The topological surface states can also play a vital role in facilitating surface reactions by serving as an effective electron bath, which may provide new design of heterogeneous catalysts [19]. TIs have also shown promise for thermoelectric applications [20].The TIs discovered so far include simple semimetals (Sb and Bi) [ 4,[21][22][23][24][25][26][27][28][29], alloys (Bi1 − xSbx) [4,16], binary compounds (HgTe, Bi2Se3, Sb2Te3, and Bi2Te3) [4-10, 20, 30-36], and ternary semiconducting Heusler compounds [12][13][14]. As a simple elemental TI, semimetal Sb has the same nontrivial topological order as Bi1 − xSbx for x > 0.07 [4,21].…”

“…As a simple elemental TI, semimetal Sb has the same nontrivial topological order as Bi1 − xSbx for x > 0.07 [4,21]. Two Rashba-type spin-split surface bands on Sb(111), connected to the bulk conduction and the valence bands separately, result in a single Dirac cone within the bulk bandgap of Sb [21][22][23][24][25][26][27][28][29]. Importantly, Sb(111) thin films with a thickness of ≤15 bilayers (BL; with 1 BL = 3.75 Å) can be converted into a 3D TI due to the quantum confinement effect which opens up a positive bandgap for the bulk states [24][25][26].…”