Coherent topological transport on the surface of Bi2Se3

Kim, Dohun; Syers, Paul; Butch, Nicholas P.; Paglione, Johnpierre; Fuhrer, Michael S.

doi:10.1038/ncomms3040

Cited by 133 publications

(164 citation statements)

References 33 publications

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“…QL according to an ARPES study [51], such a transition is naturally expected when the Fermi level is tuned into this gap and was experimentally confirmed by D. Kim et al [50]. However, similar transitions were observed even in films with their Fermi levels far above the Dirac point: first by us in Y. Kim et al [45] and later by Taskin et al [47].…”

Section: Weak Anti-localizationmentioning

confidence: 90%

“…Two experiments have made the best case for a truly depleted bulk state, one by surface-doping thin Bi 2 Se 3 flakes in conjunction with electro-static gating [50], and the other achieved with compensation-doped Bi 2 Se 3 thin-films [30]. The likely explanation as to how these experiments got around the Mott criteria is the previously mentioned use of band bending in the ultra thin limit (t < 2 × z D ).…”

Section: Weak Anti-localizationmentioning

confidence: 99%

“…The main result of both experiments is the observation that the Ã parameter transitions from 1 to 2 as the bulk state transforms from metallic to insulating state. The former experiment by D. Kim et al [50] showed that while Ã  1 regardless of thickness when the carrier density is high (≳ 5 × 10 12 /cm 2 per surface), as the carriers were depleted through gating Ã transitioned from 1 to 2 for films thicker than ~10 QL but remained at ~1 for thinner samples. that at fixed thickness (20 QL) as the bulk state was depleted by Cu doping, Ã smoothly increased from 1 to 2.…”

Section: Weak Anti-localizationmentioning

confidence: 99%

See 2 more Smart Citations

Transport properties of topological insulators: Band bending, bulk metal-to-insulator transition, and weak anti-localization

Brahlek

Koirala

Bansal

et al. 2015

Solid State Communications

142

172

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Section: Weak Anti-localizationmentioning

confidence: 90%

Section: Weak Anti-localizationmentioning

confidence: 99%

Section: Weak Anti-localizationmentioning

confidence: 99%

See 1 more Smart Citation

Transport properties of topological insulators: Band bending, bulk metal-to-insulator transition, and weak anti-localization

Brahlek

Koirala

Bansal

et al. 2015

Solid State Communications

142

172

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“…The WAL in TIs has been intensively studied both theoretically 32,33 and experimentally 16,17,21,22,[34][35][36] . The peculiar magnetic-field dependence of the electrical conductivity σ associated with WAL is described by the simplified Hikami-Larkin-Nagaoka (HLN) formula…”

mentioning

confidence: 99%

Top gating of epitaxial (Bi1−xSbx)2Te3 topological insulator thin films

Yang

Taskin

Sasaki

et al. 2014

Applied Physics Letters

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The tunability of the chemical potential for a wide range encompassing the Dirac point is important for many future devices based on topological insulators. Here we report a method to fabricate highly efficient top gates on epitaxially grown (Bi1−xSbx)2Te3 topological insulator thin films without degrading the film quality. By combining an in situ deposited Al2O3 capping layer and a SiNx dielectric layer deposited at low temperature, we were able to protect the films from degradation during the fabrication processes. We demonstrate that by using this top gate, the carriers in the top surface can be efficiently tuned from n-to p-type. We also show that magnetotransport properties give evidence for decoupled transport through top and bottom surfaces for the entire range of gate voltage, which is only possible in truly bulk-insulating samples.Topological insulators (TIs) are a class of insulators possessing an energy gap in the bulk and helically spinpolarized gapless states on the surface. [1][2][3] In the last few years, great efforts and progress have been made to synthesize high-quality, bulk-insulating TI materials in various ways. [4][5][6][7][8][9][10][11][12][13] . As the materials issues being solved, the focus and interest of experimentalists start to shift to the realization of the theoretically proposed TI devices for applications ranging from spintronics to quantum computing. 1-3 For such devices, an efficient gate control to tune the Fermi level in a wide range is usually essential, and already many gating experiments have been done on TI materials by using different gating techniques. [12][13][14][15][16][17][18][19][20] Among the various gating techniques, top gating has an advantage to provide local control of the chemical potential, which is favorable in many applications. However, a damage-free method to fabricate efficient top gates on TIs has not yet been fully developed.To achieve efficient top-gate controls of TI materials, there are two main difficulties. One is to obtain bulkinsulating samples, because the unwanted bulk carriers bring the Fermi level far away from the Dirac point and screen the electric field. This difficulty is being solved by means of chemical doping, in both single crystals 4-10,12,13 and thin films. 11 The other difficulty is the degradations of the sample surface during the fabrication processes, especially during the deposition of the dielectric material. It has been shown that the usual methods to deposit dielectric materials such as atomic layer deposition (ALD) can cause heavy damage to the TI surface; 15 such a damage would lower the surface mobility and also introduce a large number of impurity states to pin the surface chemical potential, making its gate tuning to be difficult. 15 It is thus important to develop a method to fabricate top gates with minimal damage to the TI surface.In this Letter, we report our top-gating results on (Bi 1−x Sb x ) 2 Te 3 topological-insulator thin films grown by molecular beam epitaxy (MBE). Following Ref. 11, the composition of ...

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“…In TI thin films, however, multiple channels could be involved in the transport due to the existence of the top and bottom surface states, as well as possible conducting bulk. Nevertheless, α ≈ 1/2 has often been observed in TI thin films due to the coupling between various conducting channels [26,31,[44][45][46][47][48][49][50][51].…”

mentioning

confidence: 99%

Observation of Anderson Localization in Ultrathin Films of Three-Dimensional Topological Insulators

Liao

Feng

et al. 2015

Phys. Rev. Lett.

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Anderson localization, the absence of diffusive transport in disordered systems, has been manifested as hopping transport in numerous electronic systems, whereas in recently discovered topological insulators it has not been directly observed. Here we report experimental demonstration of a crossover from diffusive transport in the weak antilocalization regime to variable range hopping transport in the Anderson localization regime with ultrathin (Bi1−xSbx)2Te3 films. As disorder becomes stronger, negative magnetoconductivity due to the weak antilocalization is gradually suppressed, and eventually positive magnetoconductivity emerges when the electron system becomes strongly localized. This works reveals the critical role of disorder in the quantum transport properties of ultrathin topological insulator films, in which theories have predicted rich physics related to topological phase transitions.The concept of Anderson localization has profoundly influenced our understanding of electron conductivity [1]. While examples for disorder driven metal-insulator transition are abundant in three-dimensions (3D), the question of whether Anderson transitions exist in 2D has posed a lot of theoretical and experimental challenges. Scaling theory proposed by Abrahams et al. predicts that there are no truly metallic states in non-interacting 2D electron systems [2,3]. It was, however, discovered later that extended electron states may exist when electronelectron (e-e) interaction, spin-orbit coupling (SOC) or magnetic field comes in to play [4,5]. The 3D topological insulators (TIs) discovered in recent years [6,7] provide novel types of 2D electron systems that are of particular interest for study of the localization-delocalization problem. The Dirac surface states of 3D TIs are believed to be topologically protected from localization due to its special symmetry class [8][9][10][11][12]. Moreover, when a 3D TI thin film is sufficiently thin, the hybridization between the top and the bottom surface states opens an energy gap near the Dirac point [13], and it is suggested theoretically that the hybridization gap would drive the electron system to topologically different phase, such as a quantum spin Hall insulator or a trivial band insulator [14][15][16]. Even though a lot of work has been carried out on electron transport properties of TI thin films [17][18][19][20], the fate of such electron systems under the condition of strong disorder (or in other words, whether Anderson localization could take place), still remains unclear.In this work, we have studied electron transport in a large number of highly gate-tunable TI thin films with various thicknesses and chemical compositions. We found that only in ultrathin TI films in which surface hybridization and disorder effects are significant, hopping transport, a hallmark of strong localization [21][22][23], can be observed. The observed temperature and magnetic field dependences of conductivity suggest that electron transport can be driven from the diffusive transport governed by we...

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Coherent topological transport on the surface of Bi2Se3

Cited by 133 publications

References 33 publications

Transport properties of topological insulators: Band bending, bulk metal-to-insulator transition, and weak anti-localization

Transport properties of topological insulators: Band bending, bulk metal-to-insulator transition, and weak anti-localization

Top gating of epitaxial (Bi1−xSbx)2Te3 topological insulator thin films

Observation of Anderson Localization in Ultrathin Films of Three-Dimensional Topological Insulators

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