Tunable Dirac cone in the topological insulator Bi2-xSbxTe3-ySey

Abstract

The three-dimensional topological insulator is a quantum state of matter characterized by an insulating bulk state and gapless Dirac cone surface states. Device applications of topological insulators require a highly insulating bulk and tunable Dirac carriers, which has so far been difficult to achieve. Here we demonstrate that Bi 2-x sb x Te 3-y se y is a system that simultaneously satisfies both of these requirements. For a series of compositions presenting bulk-insulating transport behaviour, angle-resolved photoemission spectroscopy reveals that the chemical potential is always located in the bulk band gap, whereas the Dirac cone dispersion changes systematically so that the Dirac point moves up in energy with increasing x, leading to a sign change of the Dirac carriers at x~0.9. such a tunable Dirac cone opens a promising pathway to the development of novel devices based on topological insulators.

Quantum oscillations of the topological surface states in low carrier concentration crystals of Bi2−xSbxTe3Pan1, Никитин2, Wu3 et al. 2016Solid State Communications7100View full textAdd to dashboardCite

“…The composition around (x, y)=(0.50,1.3) was found to be the optimum for bulk insulating behavior, as evidenced by a resistivity of several Ωcm at liquid helium temperatures and a bulk carrier concentration of ∼ 2×10 16 cm −3 . The appealing topological properties of BSTS, notably a tunable Dirac cone, were furthermore demonstrated by ARPES [16], STM and STS [17] and THz Time Domain Spectroscopy [18]. We remark that recently also stoichiometric BiSbTeSe 2 has become an attractive material to investigate topological surface states [19,20,21].…”

Growth of High-Mobility Bi2Te2Se Nanoplatelets on hBN Sheets by van der Waals Epitaxy

“…Bi 2 Te 2 Se has emerged as one of the most promising TIs due to its simple surface band structure, large bulk band gap and low bulk contribution to the total charge transport 16,20,21 . Our Bi 2 Te 2 Se films grown by van der Waals epitaxy are sufficiently ordered to display Shubnikov-de Haas (SdH) oscillations which provide access to important quantities such as the cyclotron mass, the Fermi velocity or Fermi energy 23 .…”

Indications of surface-dominated transport in single crystalline nanoflake devices of topological insulator Bi1.5Sb0.5TeXia1, Ren2, Sulaev3 et al. 2013Phys. Rev. B136181572View full textAdd to dashboardCite

“…From the systematic decrease of resistivity with decreasing sample thickness and the energy-dispersive X-ray spectroscopy (EDS) as shown in supplementary information, we can conclude that the dramatic decrease of resistivity in nanoflake device is not due to chemical inhomogeneity. As the material system has already been proved to be a topological insulator 36,37 , the dramatic decrease of resistivity with decreasing sample thickness in nanoflake devices indicates that the contribution from the surface states plays a more and more important role as the thickness reduces. Suppose the total thickness of the two surface states is 5 nm, we use a simple model (supplementary information) to fit the resistivity of the surface states and bulk.…”

“…Realizing surface dominated transport in current topological insulator systems is still a challenge despite extensive efforts involving chemical doping 22,[33][34][35][36][37][38][39] , thin film or nanostructure fabricating [25][26][27][28][29][30][31][32] and electrical gating 21,26,32 .…”