Direct Observation of Broken Time-Reversal Symmetry on the Surface of a Magnetically Doped Topological Insulator

Okada, Yoshinori; Dhital, Chetan; Zhou, Wenwen; Huemiller, Erik; Lin, Hsin; Basak, S.; Bansil, Arun; Huang, Yaobo; Ding, Hong; Wang, Z.; Wilson, Stephen D.; Madhavan, Vidya

doi:10.1103/physrevlett.106.206805

Cited by 159 publications

(158 citation statements)

References 25 publications

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“…1c, that has previously been identified as the energy of the bottom of the surface-projected conduction band at the Γ point as shown in Fig. 1b via a comparison between STM and angleresolved photoemission spectroscopy data [31][32][33][34] . Tracking the energy of E* allows us to follow spatial shifts in the bulk bands with respect to the Fermi energy.…”

Section: Topography Of Rippled Bi 2 Tementioning

confidence: 88%

“…The arrows show the approximate position for the Dirac point (E DP ) and the bulk conduction band edge around Γ point, E*. The association of the resonance feature in the sTm dI/dV spectra with the conduction band edge was determined in previous sTm studies [31][32][33] effect on the Dirac dispersion. Our studies suggest that generating ripples provides an avenue to engineer the potential landscape in TIs.…”

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confidence: 82%

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Ripple-modulated electronic structure of a 3D topological insulator

et al. 2012

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3D topological insulators, similar to the Dirac material graphene, host linearly dispersing states with unique properties and a strong potential for applications. A key, missing element in realizing some of the more exotic states in topological insulators is the ability to manipulate local electronic properties. Analogy with graphene suggests a possible avenue via a topographic route by the formation of superlattice structures such as a moiré patterns or ripples, which can induce controlled potential variations. However, while the charge and lattice degrees of freedom are intimately coupled in graphene, it is not clear a priori how a physical buckling or ripples might influence the electronic structure of topological insulators. Here we use Fourier transform scanning tunneling spectroscopy to determine the effects of a one-dimensional periodic buckling on the electronic properties of Bi 2 Te 3. By tracking the spatial variations of the scattering vector of the interference patterns as well as features associated with bulk density of states, we show that the buckling creates a periodic potential modulation, which in turn modulates the surface and the bulk states. The strong correlation between the topographic ripples and electronic structure indicates that while doping alone is insufficient to create predetermined potential landscapes, creating ripples provides a path to controlling the potential seen by the Dirac electrons on a local scale. Such rippled features may be engineered by strain in thin films and may find use in future applications of topological insulators.

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Section: Topography Of Rippled Bi 2 Tementioning

confidence: 88%

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confidence: 82%

Ripple-modulated electronic structure of a 3D topological insulator

et al. 2012

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“…All these materials have approximately similar elemental compositions and lattice dimensions; the structural features and corrugations are expected to be similar. However, the electronic contribution to STM topographs in TIs, which typically manifests as aperiodic inhomegenous patches, is notable in Bi 2 X 3 [17,41] and provides the dominant contribution to the topographs in Bi x Sb 1−x [39]. Such electronic inhomogeneity in TIs is understood to be associated with poorly screened bulk defects [17].…”

Section: Stm Topographymentioning

confidence: 99%

“…4a, [45]) forming a hexagonal lattice with the [17]; and (d) doped Bi2Te3 [41]. All three topographs show aperiodic modulations attributed to chemical potential fluctuations [17].…”

Section: Stm Topographymentioning

confidence: 99%

“…In fact, LL spectroscopy and QPI imaging have shed light on several aspects of Dirac materials. For example, they have been used to visualize the absence and onset of backscattering in topological materials [39][40][41], pseudospin protection in graphene [38,42] and chemical potential fluctuations in a range of materials [17,42,43]. While each of these techniques offers great promise on its own for measuring simpler band structures, the synergistic utilization of LLs and QPI could also enable the determination of multi-component band structures.…”

Section: Quasiparticle Interferencementioning

confidence: 99%

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Momentum-resolved STM studies of Rashba-split surface states on the topological semimetal Sb

Soumyanarayanan

Hoffman

2015

Journal of Electron Spectroscopy and Related Phenomena

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Topological materials host protected surface states with locked spin and momentum degrees of freedom. The helical Dirac character of the surface states, of tremendous scientific interest, stems from the interplay of the bulk band structure and surface Rashba spin-orbit interaction. The semimetal Sb offers a pristine platform to examine the Rashba origins of the Dirac-like topological surface states. Here we present an overview of our momentum-resolved scanning tunneling spectroscopy studies of Sb, over an extended (300 meV) energy range, revealing several features characteristic of the emergence of the Dirac-like surface states from a conventional Rashba-type parabolic dispersion. Our work provides a conceptual framework to create and investigate tunable Rashba states with topological properties.

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Topological Insulators, Topological Dirac semimetals, Topological Crystalline Insulators, and Topological Kondo Insulators

Hasan

Neupane

2015

Topological Insulators

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IntroductionTopological phases of matter differ from conventional materials in that the former feature a nontrivial topological invariant in their bulk electronic wavefunction space [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. The experimental discoveries of the two-dimensional (2D) integer and fractional quantum Hall (IQH and FQH) states [15][16][17][18][19] in the 1980s realized the first two topological phases of matter in nature. These 2D topological systems are insulators in the bulk because the Fermi level is located in the middle of two Landau levels. On the other hand, the edges of these 2D topological insulators (TIs) (IQH and FQH) feature chiral 1D metallic states, leading to remarkable quantized charge transport phenomena. The quantized transverse magneto-conductivity = ne 2 ∕h (where e is the electric charge and h is the Planck constant) can be probed by charge transport experiements, which also provides a measure of the topological invariant (the Chern number) n that characterizes these quantum Hall states [20,21]. In 2005, theoretical advances [22, 23] predicted a third type of 2D TI, the quantum spin Hall (QSH) insulator. Such a topological state is symmetry-protected. A QSH insulator can be viewed as two copies of quantum Hall systems that have magnetic fields in the opposite direction. Therefore, no external magnetic field is required for the QSH phase, and the pair of quantum-Hall-like edge modes are related by the time-reversal (TR) symmetry (Figure 4.1). In 2007, the QSH phase was experimentally demonstrated in the (Hg, Cd)Te quantum wells using charge transport by measuring a longitudinal conductance of about 2e 2 ∕h (two copies of quantum Hall currents) at millikelvin temperatures [24]. The topological number that describes the QSH phase is a Z 2 invariant (ν). The Z 2 invariant can only take two values, 0 or 1, where ν = 0(1) is topologically trivial (nontrivial).However, it is important to note that the 2D topological (IQH, FQH, and QSH) insulators are realized only at buried interfaces of ultraclean semiconductor

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Direct Observation of Broken Time-Reversal Symmetry on the Surface of a Magnetically Doped Topological Insulator

Cited by 159 publications

References 25 publications

Ripple-modulated electronic structure of a 3D topological insulator

Ripple-modulated electronic structure of a 3D topological insulator

Momentum-resolved STM studies of Rashba-split surface states on the topological semimetal Sb

Topological Insulators, Topological Dirac semimetals, Topological Crystalline Insulators, and Topological Kondo Insulators

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