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      Tuning insulator-semimetal transitions in 3D topological insulator thin films by inter-surface hybridization and in-plane magnetic fields

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          Abstract

          A pair of Dirac points (analogous to a vortex-antivortex pair) associated with opposite topological numbers (with \(\pm\pi\) Berry phases) can be merged together through parameter tuning and annihilated to gap the Dirac spectrum, offering a canonical example of a topological phase transition. Here, we report transport studies on thin films of BiSbTeSe\(_2\) (BSTS), which is a 3D TI that hosts spin-helical gapless (semi-metallic) Dirac fermion surface states (SS) for sufficiently thick samples, with an observed resistivity close to \(h/4e^2\) at the charge neutral point. When the sample thickness is reduced to \(\sim\)10 nm thick, the Dirac cones from the top and bottom surfaces can hybridize (analogous to a "merging" in the real space) and become gapped to give a trivial insulator. Furthermore, we observe that an in-plane magnetic field can drive the system again towards a metallic behavior, with a prominent negative magnetoresistance (MR, up to \(\sim\)$-\(95\%) and a temperature-insensitive resistivity close to \)h/2e^2$ at the charge neutral point. The observation is interpreted in terms of a predicted effect of an in-plane magnetic field to reduce the hybridization gap (which, if small enough, may be smeared by disorder and a metallic behavior). A sufficiently strong magnetic field is predicted to restore and split again the Dirac points in the momentum space, inducing a distinct 2D topological semimetal (TSM) phase with 2 single-fold Dirac cones of opposite spin-momentum windings.

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          Microscopic investigation of Bi2-xSbxTe3-ySey systems: On the origin of a robust intrinsic topological insulator

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            Author and article information

            Journal
            07 April 2019
            Article
            1904.03722
            35762a94-dc29-4b97-b9f0-6ebacbb7d8ba

            http://arxiv.org/licenses/nonexclusive-distrib/1.0/

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            Custom metadata
            4 figures and 5 pages for main text, 13 pages for supplementary information
            cond-mat.mes-hall

            Nanophysics
            Nanophysics

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