A topological insulator surface under strong Coulomb, magnetic and disorder perturbations
Open accessAbstract
Topological insulators embody a state of bulk matter characterized by spin-momentum-locked surface states that span the bulk bandgap. This highly unusual surface spin environment provides a rich ground for uncovering new phenomena. Understanding the response of a topological surface to strong Coulomb perturbations represents a frontier in discovering the interacting and emergent many-body physics of topological surfaces. Here we present the first controlled study of topological insulator surfaces under Coulomb and magnetic perturbations. We have used time-resolved deposition of iron, with a large Coulomb charge and significant magnetic moment, to systematically modify the topological spin structure of the Bi_2Se_3 surface. We observe that such perturbation leads to the creation of odd multiples of Dirac fermions and that magnetic interactions break time-reversal symmetry in the presence of band hybridizations. We present a theoretical model to account for the observed electron dynamics of the topological surface. Taken collectively, these results are a critical guide in controlling electron mobility and quantum behaviour of topological surfaces, not only for device applications but also in setting the stage for creating exotic particles such as axions or imaging monopoles on the surface.
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- Findingown data
A theoretical simulation of a non-magnetic surface Coulomb perturbation on Bi2Se3 qualitatively reproduces the progressive appearance of new Dirac points with increasing iron deposition.
“Theoretical simulation of non-magnetic surface Coulomb perturbation on Bi 2 Se 3 is shown in Fig. 3a, and qualitatively reproduces the progressive appearance of new Dirac points with increasing iron deposition.”
Quote in the paperSubstantial claim - Findingown data
After heavy iron deposition, the surface electronic structure of Bi2Se3 is greatly altered, indicating a significant change in the surface electronic environment.
“As seen in Fig. 1d the surface electronic structure after heavy iron deposition is greatly altered, showing that a significant change in the surface electronic environment has been achieved.”
Quote in the paperSubstantial claim - Findingown data
In sample no 2, when the chemical potential is above the bulk conduction-band minimum, new surface states disperse across the full bulk bandgap.
“When the chemical potential is positioned above the bulk conduction-band minimum, as in sample no 2 (Fig. 2c), the dispersion of new surface states across the full bulk bandgap is visible within the photoemission image.”
Quote in the paperSubstantial claim - Findingown data
The Rashba description is accurate for Bi2Se3 only in a small region around the Brillouin zone centre, because at larger momenta the electronic states pair off and are nearly spin degenerate.
“Our data and simulations show that this description is only accurate for Bi 2 Se 3 in a small part of the Brillouin zone surrounding the Brillouin zone centre, because at momenta further from the point the electronic states pair off and are nearly spin degenerate (see Fig. 3b).”
Quote in the paperSubstantial claim - Findingown data
Electron velocities near the D1 and D2 Dirac points increase monotonically as iron is added.
“Electron velocities (band slope) near the D1 and D2 Dirac points increase monotonically as iron is added”
Quote in the paperSubstantial claim
- Findingown data
Modifying a GGA numerical prediction of the D0 surface state by adding perturbative coupling to a surface layer of magnetic impurities with ferromagnetic out-of-plane order yields a dispersion that closely matches the experimental data.
“Figure 4a shows the result of modifying a generalized gradient approximation (GGA) numerical prediction of the D0 surface state by adding perturbative coupling to a surface layer of magnetic impurities with ferromagnetic out-of-plane order (equivalent to the Zeeman effect), yielding a dispersion that closely matches the experimental data.”
Quote in the paperSubstantial claim - Findingown data
Numerical simulations show that new D1 and D2 Dirac-point electrons are localized deeper inside the material than D0.
“Our numerical simulations have shown that the new D1 and D2 Dirac-point electrons are localized deeper inside the material than D0”
Quote in the paperSubstantial claim - Findingown data
The D0 gap is visible at different incident photon energies, confirming it is a surface feature rather than a bulk band-structure feature.
“This gap can be seen clearly at different incident photon energies in Fig. 2d, confirming that it is a feature of the surface and not the bulk electronic band structure.”
Quote in the paperSubstantial claim - Findingown data
The number of surface bands intersecting the Fermi level between Γ and M progresses from one to three to five, with one band from D0 and two more from each new D1 and D2 Dirac point.
“The number of surface bands intersecting the Fermi level between the and M points progresses from one to three to five, with one band contributed by the original (D0) Dirac cone and two more bands contributed by each of the new (D1, D2) Dirac points.”
Quote in the paperSubstantial claim - Findingown data
After about six minutes of iron deposition on p-type sample no 1, new surface states appear at the Fermi level, with new Dirac points D1 and D2 above the original D0 Dirac cone.
“After approximately six minutes of deposition, new surface states that do not exist in unperturbed samples become visible at the Fermi level, with new Dirac points labelled D1 and D2 above the Dirac cone that is seen in as-grown Bi 2 Se 3 (D0).”
Quote in the paperSubstantial claim - Findingown data
After about six minutes of deposition, a gap becomes apparent at the D0 Dirac node, separating the upper and lower Dirac cones of the original surface state.
“It is also after approximately six minutes of deposition that a gap begins to be apparent at the D0 Dirac node, shown by a parabolic shape near the Dirac node, separating the upper and lower Dirac cones of the original surface state.”
Quote in the paperSubstantial claim - Findingown data
The signature of large ferromagnetic domains with in-plane moment is a twin-peak feature that is not seen in the data.
“The signature of large ferromagnetic domains with in-plane moment is a twin-peak feature that is not seen in the data.”
Quote in the paperSubstantial claim - Interpretationown data
Iron increases the Rashba interaction term in the theoretical models.
“showing that iron is increasing the 'Rashba' interaction term ((k× ẑ)•σ, with σ representing the Pauli matrices) identified in theoretical models 3 .”
Quote in the paperSubstantial claim0 of 1 sources checked- cites [3] Fu, L., Kane, C. L. & Mele, E. J. Topological insulators in three dimensions. Phys. Rev. Lett. 98, 106803 (2007). source
Not checked in the free run.
- Interpretationreasoning
D1 and D2 electrons are expected to interact more weakly with electronic orbitals of surface-deposited iron.
“and are expected to interact more weakly with electronic orbitals of the surface-deposited iron.”
Quote in the paperSubstantial claim - Interpretationown data
The progression to an odd number of Dirac states is consistent with the Mod(2) character of surface electrons on a crystal with bulk topological insulator order.
“This is consistent with the Mod(2) character of surface electrons on a crystal with bulk topological insulator order, that the topological surface likes to maintain an odd number of Dirac states.”
Quote in the paperSubstantial claim - Interpretationreasoning
The reduction in δk as the gap appears is probably indicative of a magnetic disorder-to-order transition that reduces scattering.
“the reduction in δk as the gap appears is probably indicative of a magnetic disorder-to-order transition, leading to a reduction in scattering.”
Quote in the paperSubstantial claim - Interpretationown data
Reducing the prevalence of magnetic domains with in-plane moment could also make surface-state bands appear narrower even if electronic mean free paths are unchanged, as seen by comparing domain-averaged band profiles.
“Reducing the prevalence of magnetic domains with in-plane moment could also cause the surface-state bands to seem narrower even if electronic mean free paths are unchanged, as can be observed through comparing the domain-averaged band profiles in Fig. 3d.”
Quote in the paperNot a substantial claim - Interpretationreasoning
The appearance of the D0 gap in the data is consistent with a scenario in which much of the iron-deposited crystal surface is occupied by domains with net out-of-plane magnetic moment.
“The appearance of a gap at D0 in our data is therefore consistent with a scenario in which much of the iron-deposited crystal surface is occupied by domains that have net out-ofplane magnetic moment.”
Quote in the paperSubstantial claim- Rests on an assumption: Global ferromagnetism breaks time-reversal symmetry, making it possible to induce a gap at the Dirac point, which is otherwise disallowed by crystal symmetry.
- May combine two claims. 25
- Classified as probably not a substantial claim. 9
May combine two claims.
Findingown dataIn both samples, positively charged Fe surface ions progressively lower the surface-state energy and cause new surface states with energy-momentum contours similar to the bottom of the bulk conduction band.
“In each case, it is observed that the presence of positively charged Fe surface ions progressively lowers the energy of the surface state and causes the appearance of new surface states with energy-momentum contours similar to the bottom of the bulk conduction band.”
Quote in the paperSubstantial claimMay combine two claims.
Findingown dataA gap appears at the D0 Dirac point after heavy iron deposition, and the lower D0 Dirac cone acquires a buckled shape with a local energy minimum at zero momentum.
“A gap appears at the D0 Dirac point after heavy iron deposition, and the lower D0 Dirac cone acquires a buckled shape with a local energy minimum at zero momentum.”
Quote in the paperSubstantial claimMay combine two claims.
Findingown dataEvidence of Landau levels is neither seen in the data nor expected from theory.
“Evidence of Landau levels is neither seen in our data nor in this context expected from theory.”
Quote in the paperSubstantial claimMay combine two claims.
Findingown dataSample no 1 before deposition is slightly p-type with resistivity ρ = 23 mΩ cm, and sample no 2 is electron-doped from Se vacancy defects.
“The bulk electronic state of sample no 1 before deposition is slightly p type with significant resistivity (ρ = 23 m cm), and sample no 2 is electron doped from Se vacancy defects in as-grown Bi 2 Se 3 .”
Quote in the paperSubstantial claimMay combine two claims.
Findingown dataThe new low-energy features have no z-axis momentum dependence, confirming they are largely two-dimensional.
“Unlike the bulk electronic states of Bi 2 Se 3 (ref.22), these features have no z-axis momentum dependence, confirming that they are largely two dimensional in nature (Fig. 1e).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites [22] Wray, L. A., Xu, S-Y., Xia, Y., Hor, Y. S., Qian, D., Fedorov, A. V., Lin, H., Bansil, A., Cava, R. J. & Hasan, M. Z. Observation of topological order in a superconducting doped topological insulator. Nature Phys. 6, 855–859 (2010). source
Not checked in the free run.
May combine two claims.
Findingown dataIn sample no 2, after five minutes of Fe deposition a new strongly split surface band with a D1 Dirac point at Γ appears, but no D2 bands appear after longer deposition.
“A new, strongly split surface band is observed in sample no 2 after five minutes of Fe deposition with a (D1) Dirac point at the point, but no further (for example, D2) bands appeared after longer deposition.”
Quote in the paperSubstantial claimMay combine two claims.
Findingown dataExperimentally observed surface states begin to pair off at momentum separation greater than about 0.1 Å−1 from the Brillouin zone centre, with upper D0 approaching degeneracy with lower D1 and upper D1 connecting to lower D2.
“Through comparison with our numerical result, we can see that the experimentally observed surface states begin to pair off at momentum separation greater than ∼0.1 Å -1 from the Brillouin zone centre, with the upper D0 Dirac cone approaching degeneracy with the lower D1 band, and the upper D1 band connecting to the lower D2 band.”
Quote in the paperSubstantial claimMay combine two claims.
Findingown dataThe mass induced in the upper D0 Dirac cone after full deposition is approximately 0.1 electron masses, and the surface bandgap is about 100 meV.
“The mass induced in the upper D0 Dirac cone after full deposition is approximately 0.1 M e (electron masses), and the surface bandgap is about 100 meV.”
Quote in the paperSubstantial claimMay combine two claims.
Findingown dataAfter 12 minutes of deposition, the D0 Dirac point binding energy sank by about 0.6 eV, and further deposition did not change electron binding energies.
“After 12 min of deposition, the binding energy of the D0 Dirac point was found to have sunk by approximately 0.6 eV in energy, and the electron binding energies ceased to change under further deposition.”
Quote in the paperSubstantial claimMay combine two claims.
Findingown dataFive surface bands, an odd number, intersect the Fermi level after heavy iron deposition, rather than one, and extend below the Fermi level as multiple Dirac cones.
“Five (odd number of) surface bands intersect the Fermi level rather than just one, and extend below the Fermi level in the form of multiple Dirac cones.”
Quote in the paperSubstantial claimMay combine two claims.
Findingown dataThe photoemission image becomes qualitatively sharper with increasing iron coverage in a certain regime, corresponding approximately to increasing clarity of the D0 gap.
“Contrary to the usual trend of deposition experiments, in which photoemission images become increasingly blurry as molecules are haphazardly added to the surface, we identify a regime in which the image becomes qualitatively sharper with the increasing coverage of iron (seen in Fig. 4d and the first three panels of Fig. 2a), corresponding approximately to the increasing clarity of the D0 gap.”
Quote in the paperSubstantial claimProbably not a substantial claim: may not pass S3 (load-bearing).
Findingown dataDoping evolution of the lower D0 Dirac cone is much less clear in the data because of the disordered surface and close proximity of features.
“Doping evolution of the lower D0 Dirac cone is much less clear in the data, owing to the disordered surface and close proximity of features.”
Quote in the paperNot a substantial claimProbably not a substantial claim: may not pass S3 (load-bearing).
PremisecitationMagnetic interactions in Bi2Se3 can be controlled through magnetic ions such as Fe or Mn.
“magnetic interactions can be controlled through magnetic ions such as Fe or Mn (refs 9, 10).”
Quote in the paperNot a substantial claim0 of 2 sources checked- cites [9] Hor, Y. S. et al. Development of ferromagnetism in the magnetically doped topological insulator Bi2−xMnxTe3 . Phys. Rev. B 81, 195203 (2010). source
Not checked in the free run.
- cites [10] Hsieh, D. et al. Observation of time-reversal-protected single-Dirac-cone topological-insulator states in Bi2Te3 and Sb2Te3 . Phys. Rev. Lett. 103, 146401 (2009). source
Not checked in the free run.
May combine two claims.
InterpretationcitationBecause magnetic-field perturbations from the submonolayer iron coating are weak, the magnetic-phase term in perturbative Hamiltonians can be discounted, and the dominant magnetic effects are expected to be described by a local Heisenberg-exchange term representing direct wavefunction overlap between surface electrons and spin-polarized Fe 3d orbitals.
“Because magnetic-field perturbations from the submonolayer iron coating are quite weak, the magnetic-phase term in perturbative Hamiltonians can be discounted, and the dominant magnetic effects are expected to be described by a local Heisenberg-exchange term representing direct wavefunction overlap (hopping) between surface electrons and spin-polarized Fe 3d orbitals 11 .”
Quote in the paperSubstantial claim0 of 1 sources checked- cites [11] Biswas, R. R. & Balatsky, A. V. Impurity-induced states on the surface of 3D topological insulators. Phys. Rev. B 81, 233405 (2010). source
Not checked in the free run.
May combine two claims.
PremisecitationSurface electrons in Bi2Se3 form a Dirac cone spanning the bulk insulating gap and consist of spin-momentum-locked helical states.
“Spinresolved photoemission studies reveal that surface electrons in Bi 2 Se 3 form a Dirac cone spanning the bulk insulating gap, composed of spin-momentum-locked helical states (Fig. 1a).”
Quote in the paperSubstantial claimMay combine two claims.
Premiseown dataPlacing the Fermi level at the Dirac point in the presence of bulk magnetic impurities can produce a small gap at the Fermi level, but its full character cannot be decisively resolved because of lineshape broadening.
“Placing the Fermi level at the Dirac point in the presence of magnetic impurities in the bulk can lead to a small gap at the Fermi level (Fig. 1b); however, the full character of this gap cannot be decisively resolved owing to the lineshape broadening effects.”
Quote in the paperSubstantial claimClassified as probably not a substantial claim.
PremisecitationTopological insulators are a state of bulk matter with spin-momentum-locked surface states that span the bulk bandgap.
“Topological insulators embody a state of bulk matter characterized by spin-momentum-locked surface states that span the bulk bandgap 1-7 .”
Quote in the paperSubstantial claim0 of 7 sources checked- cites [1] Moore, J. E. Topological insulators: The next generation. Nature Phys. 5, 378–380 (2009). source
Not checked in the free run.
- cites [2] Hasan, M. Z. & Kane, C. L. Topological insulators. Rev. Mod. Phys. 82, 3045–3067 (2010). source
Not checked in the free run.
- cites [3] Fu, L., Kane, C. L. & Mele, E. J. Topological insulators in three dimensions. Phys. Rev. Lett. 98, 106803 (2007). source
Not checked in the free run.
- cites [4] Hsieh, D. et al. A topological Dirac insulator in a quantum spin Hall phase. Nature 452, 970–974 (2008). source
Not checked in the free run.
- cites [5] Hsieh, D. et al. Observation of unconventional quantum spin textures in topological insulators. Science 323, 919–922 (2009). source
Not checked in the free run.
- cites [6] Hsieh, D. et al. A tunable topological insulator in the spin helical Dirac transport regime. Nature 460, 1101–1105 (2009). source
Not checked in the free run.
- cites [7] Xia, Y. et al. Observation of a large-gap topological-insulator class with a single Dirac cone on the surface. Nature Phys. 5, 398–402 (2009). source
Not checked in the free run.
May combine two claims.
PremisecitationIn a normal three-dimensional material, electrons interacting with surface-deposited magnetic impurities can scatter away from the surface over a 2π solid angle, so two-dimensional magnetic interactions typically decay over several ångstroms.
“In a normal three-dimensional material, electrons that interact with surface-deposited magnetic impurities are free to scatter away from the surface over a 2π solid angle, and the two-dimensional magnetic interactions therefore typically decay over several ångstroms (see, for example, ref. 27).”
Quote in the paperSubstantial claim0 of 1 sources checked- cites [27] Wahl, P. et al. Exchange interaction between single magnetic adatoms. Phys. Rev. Lett. 98, 056601 (2007). source
Not checked in the free run.
May combine two claims.
Interpretationown dataIf the D0 bandgap were due to an isotropic out-of-plane magnetic field, a similar gap would be expected at the D1 and D2 Dirac points, which is not observed.
“If the D0 bandgap were due to an isotropic out-of-plane magnetic field, a similar gap would be expected at the D1 and D2 Dirac points, which is clearly not observed.”
Quote in the paperSubstantial claimClassified as probably not a substantial claim.
PremisecitationThe spin-splitting of topological surface bands is often described as a special case of the Rashba effect, where surface states become spin-split by an energy proportional to momentum k.
“The spin-splitting of topological surface bands is often discussed as a special case of the Rashba effect (see, for example, refs 3,20), in which surface electronic states become spin-split by an energy proportional to their momentum k.”
Quote in the paperSubstantial claim0 of 2 sources checkedMay combine two claims.
PremisecitationIron deposited on a Se-terminated Bi2Se3 surface is expected to form a mild chemical bond, occupy an ionization state between 2+ and 3+, and have roughly 4 μB magnetic moment.
“Iron deposited on a Se 2-surface is expected to form a mild chemical bond, occupying a large ionization state between 2 + and 3 + with roughly 4 µ B magnetic moment 25 .”
Quote in the paperNot a substantial claim0 of 1 sources checked- cites [25] Kawaminami, M. & Okazaki, A. Neutron diffraction study of Fe7Se8. II. J. Phys. Soc. Jpn 29, 649–655 (1970). source
Not checked in the free run.
May combine two claims.
PremisecitationThe origin of the topological insulator state in Bi2Se3 is a symmetry inversion at Γ, and electronic states near the Brillouin-zone boundary resemble those of topologically trivial materials.
“This can be understood because the origin of the topological insulator state in Bi 2 Se 3 is a symmetry inversion that occurs at the point 7,18 , and the electronic states close to the Brillouin-zone boundary are similar to those of topologically trivial materials.”
Quote in the paperSubstantial claim0 of 2 sources checked- cites [7] Xia, Y. et al. Observation of a large-gap topological-insulator class with a single Dirac cone on the surface. Nature Phys. 5, 398–402 (2009). source
Not checked in the free run.
- cites [18] Zhang, H. et al. Model Hamiltonian for topological insulators. Phys. Rev. B 82, 045122 (2010). source
Not checked in the free run.
May combine two claims.
InterpretationcitationThe exact time at which the bandgap appears is difficult to identify, probably because there is no long-range order of iron spins on the surface and differently ordered domains contribute differently gapped signals.
“It is difficult to identify the exact time at which the bandgap appears, probably because there is no long-range order of iron spins on the surface 28,29 , and differently ordered domains will yield differently gapped contributions to the photoemission signal.”
Quote in the paperNot a substantial claim0 of 2 sources checked- cites [28] Mermin, N. D. & Wagner, H. Absence of ferromagnetism or antiferromagnetism in one- or two-dimensional isotropic Heisenberg models. Phys. Rev. Lett. 17, 1133–1136 (1966). source
Not checked in the free run.
- cites [29] Zhang, R-J. & Willis, R. F. Thickness-dependent Curie temperatures of ultrathin magnetic films: Effect of the range of spin–spin interactions. Phys. Rev. Lett. 86, 2665–2668 (2001). source
Not checked in the free run.
May combine two claims.
Interpretationnone givenThe role of magnetic domains in reshaping low-energy band structure is expected to be more subtle than Coulomb perturbations and may be limited to changes near Dirac points and self-energy lineshape effects.
“The role of magnetic domains in reshaping low-energy band structure is expected to be more subtle than Coulomb perturbations, and may be limited to changes near the Dirac points and in self-energy lineshape effects (see Fig. 3c,d).”
Quote in the paperSubstantial claimClassified as probably not a substantial claim.
Premisenone givenThe Fermi level of as-grown Bi2Se3 crystals is usually located in the bulk conduction band because of selenium vacancy defects.
“The Fermi level of grown crystals is usually found to be located in the bulk conduction band due to selenium vacancy defects;”
Quote in the paperSubstantial claimClassified as probably not a substantial claim. May combine two claims.
PremisecitationIn topological insulators, surface-state electrons are confined to two-dimensional Dirac cones, and interactions between deposited impurities are suggested to be mediated over many nanometres.
“In topological insulators, surface-state electrons are naturally confined to the surface in two-dimensional Dirac cones, and it is suggested that interactions between deposited impurities can be mediated over many nanometres (see the illustration in Fig. 4c; refs 11,26).”
Quote in the paperSubstantial claim0 of 2 sources checked- cites [11] Biswas, R. R. & Balatsky, A. V. Impurity-induced states on the surface of 3D topological insulators. Phys. Rev. B 81, 233405 (2010). source
Not checked in the free run.
- cites [26] Liu, Q. et al. Magnetic impurities on the surface of a topological insulator. Phys. Rev. Lett. 102, 156603 (2009). source
Not checked in the free run.
May combine two claims.
PremisecitationCa doping or NO2 surface deposition can place the Fermi level at the Dirac point and reach the topological transport regime.
“with Ca doping or NO 2 surface deposition the Fermi level can be placed at the Dirac point, reaching the topological transport regime 6”
Quote in the paperSubstantial claim0 of 1 sources checked- cites [6] Hsieh, D. et al. A tunable topological insulator in the spin helical Dirac transport regime. Nature 460, 1101–1105 (2009). source
Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing).
Study design and conductcitationMomentum along the z axis was determined using an inner potential of 9.5 eV, consistent with previous photoemission investigations of undoped Bi2Se3.
“Momentum along the ẑ axis is determined using an inner potential of 9.5 eV, consistent with previous photoemission investigations of undoped Bi 2 Se 3 (refs 7,22).”
Quote in the paperNot a substantial claim0 of 2 sources checked- cites [7] Xia, Y. et al. Observation of a large-gap topological-insulator class with a single Dirac cone on the surface. Nature Phys. 5, 398–402 (2009). source
Not checked in the free run.
- cites [22] Wray, L. A., Xu, S-Y., Xia, Y., Hor, Y. S., Qian, D., Fedorov, A. V., Lin, H., Bansil, A., Cava, R. J. & Hasan, M. Z. Observation of topological order in a superconducting doped topological insulator. Nature Phys. 6, 855–859 (2010). source
Not checked in the free run.
May combine two claims.
PremisecitationOut-of-plane magnetic order causes a gap in topological Dirac surface electrons, while in-plane magnetic domains cause bands to shift in momentum space.
“The general effect of Zeeman-type magnetic symmetry breaking on topological Dirac surface electrons is shown in Fig. 3c, illustrating that out-of-plane magnetic order will cause a gap, and in-plane magnetic domains will cause bands to shift in momentum space 12 .”
Quote in the paperSubstantial claim0 of 1 sources checked- cites [12] Garate, I. & Franz, M. Inverse spin-galvanic effect in a topological-insulator/ferromagnet interface. Phys. Rev. Lett. 104, 146802 (2010). source
Not checked in the free run.
Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.
Study design and conductown dataARPES measurements had energy resolution better than 15 meV and angular resolution better than 1% of the Brillouin zone.
“ARPES measurements were made at the Advanced Light Source beamlines 10 and 12 using 35.5-48 eV photons with better than 15 meV energy resolution and overall angular resolution better than 1% of the Brillouin zone.”
Quote in the paperNot a substantial claimMay combine two claims.
Interpretationown dataThe apparent ordering transition is driven by magnetic interactions mediated by the topological surface state, indicating how strong topological insulator order changes the physical environment of the material surface.
“This apparent ordering transition driven by magnetic interactions that are mediated by the topological surface state is an indication of how strong topological insulator order changes the physical environment of the material surface.”
Quote in the paperSubstantial claimProbably not a substantial claim: may not pass S3 (load-bearing).
Study design and conductown dataThe iron deposition flow rate was calibrated using a quartz microbalance with sub-ångstrom sensitivity.
“A quartz microbalance supplied by Leybold-Inficon with sub-ångstrom sensitivity was used to calibrate the iron-deposition flow rate.”
Quote in the paperNot a substantial claim
The paper relies on this without support.
No systematic surface deposition of magnetic impurities to elicit a large systematic magnetic response and controlled changes in the surface band structure had been explored.
“So far, no systematic surface deposition of magnetic impurities to elicit a large systematic magnetic response and bring about controlled changes in the surface band structure has been explored.”
The paper relies on this without support.
Bi2Se3 cleaves on the (111) selenium surface plane, providing a homogeneous environment for deposited atoms.
“Bismuth selenide cleaves on the (111) selenium surface plane, providing a homogeneous environment for deposited atoms.”
The paper relies on this without support.
Global ferromagnetism breaks time-reversal symmetry, making it possible to induce a gap at the Dirac point, which is otherwise disallowed by crystal symmetry.
“Global ferromagnetism breaks time-reversal symmetry, making it possible to induce a gap at the Dirac point, which is otherwise disallowed by the crystal symmetry.”
Claims other papers make about this one
Each is checked against this paper’s own text: does it say what the citing paper says it does?
They report key band parameters that constrain the form of the superconducting state.
“Moreover, they report key band parameters that constrain the form of the superconducting state.”
From Three-Dimensional Topological Insulators (2011) · cites this paper as [40]
Measurements of electronic band structure in Cu_xBi2Se3 (x=0 to 12%) by Wray et al. suggest that superconductivity occurs with electrons in a bulk relativistic kinematic regime and an unconventional doping mechanism causes the nontrivial topological surface character of the undoped compound to be preserved at the Fermi level of the superconducting compound, where Cooper pairing occurs.
“Measurements of electronic band structure in Cu x Bi 2 Se 3 (x=0 to 12%) by Wray et.al., (40) suggest that superconductivity occurs with electrons in a bulk relativistic kinematic regime and we identify that an unconventional doping mechanism causes the nontrivial topological surface character of the undoped compound to be preserved at the Fermi level of the superconducting compound, where Cooper”
From Three-Dimensional Topological Insulators (2011) · cites this paper as [40]
Self-check
Percentages, sums and reported differences re-computed from the paper’s own numbers.
Each contradiction between two passages listed here was confirmed by an independent check.
Caption counts five Dirac cones where the text counts three
MinorThe Figure 2 caption says iron doping creates five Dirac cones, but the text identifies three Dirac points-D0, D1 and D2-and says that five bands, not five cones, intersect the Fermi level.
“Figure 2 | Iron doping creates five helical Dirac cones.”
“The number of surface bands intersecting the Fermi level between the and M points progresses from one to three to five, with one band contributed by the original (D0) Dirac cone and two more bands contributed by each of the new (D1, D2) Dirac points.”
Cites
Topological Insulators in Three Dimensions
Fu, L., Kane, C. L., & Mele, E. J. (2007) · Physical Review Letters · doi:10.1103/physrevlett.98.106803 · Cited by 4,651 · see citing works
Observation of a large-gap topological-insulator class with a single Dirac cone on the surface
Xia, Y., Qian, D., Hsieh, D., Wray, L., Pal, A., Lin, H., Bansil, A., Grauer, D., Hor, Y. S., Cava, R. J., et al. (2009) · Nature Physics · doi:10.1038/nphys1274 · Cited by 3,765 · see citing works
Self-citationA topological Dirac insulator in a quantum spin Hall phase
Hsieh, D., Qian, D., Wray, L., Xia, Y., Hor, Y. S., Cava, R. J., & Hasan, M. Z. (2008) · Nature · doi:10.1038/nature06843 · Cited by 3,523 · see citing works
Self-citationTopological surface states protected from backscattering by chiral spin texture
Roushan, P., Seo, J., Parker, C. V., Hor, Y. S., Hsieh, D., Qian, D., Richardella, A., Hasan, M. Z., Cava, R. J., & Yazdani, A. (2009) · Nature · doi:10.1038/nature08308 · Cited by 1,052 · see citing works
Self-citationProbing Neutral Majorana Fermion Edge Modes with Charge Transport
Fu, L., & Kane, C. L. (2009) · Physical Review Letters · doi:10.1103/physrevlett.102.216403 · Cited by 566 · see citing works
Observation of topological order in a superconducting doped topological insulator
Wray, L. A., Xu, S.-Y., Xia, Y., Hor, Y. S., Qian, D., Fedorov, A. V., Lin, H., Bansil, A., Cava, R. J., & Hasan, M. Z. (2010) · Nature Physics · doi:10.1038/nphys1762 · Cited by 464 · see citing works
Self-citationExciton Condensation and Charge Fractionalization in a Topological Insulator Film
Seradjeh, B., Moore, J. E., & Franz, M. (2009) · Physical Review Letters · doi:10.1103/physrevlett.103.066402 · Cited by 267 · see citing works
Flagged first, then by citations
Research works printed but not linked: 24
- Moore, J. E. Topological insulators: The next generation. Nature Phys. 5, 378–380 (2009). · DOI · Paper page
- Hasan, M. Z. & Kane, C. L. Topological insulators. Rev. Mod. Phys. 82, 3045–3067 (2010). · DOI · Paper page
- Hsieh, D. et al. Observation of unconventional quantum spin textures in topological insulators. Science 323, 919–922 (2009). · DOI · Paper page
- Hsieh, D. et al. A tunable topological insulator in the spin helical Dirac transport regime. Nature 460, 1101–1105 (2009). · DOI · Paper page
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- Authors
- Wray, L. A., Xu, S.-Y., Xia, Y., Hsieh, D., Fedorov, A. V., Hor, Y. S., Cava, R. J., Bansil, A., Lin, H., & Hasan, M. Z.
- Affiliations
- Lawrence Berkeley National Laboratory (US)
- Princeton University (US)
- Northeastern University (US)
- Corresponding author
- Hasan, M. Zahid
- ORCID
- Venue
- Nature Physics
- Published
- 2010-12-12
- Volume
- 7
- Issue
- 1
- Pages
- 32-37
- ISSN
- 1745-2473 (ISSN-L)
- 1745-2481
- OpenAlex
- W1983721030
- Semantic Scholar
- f76d445f45350d00bad90cace328edeb0fe6eac8
- Cited by
- 581
- References
- 7
- Citations by year
- 2026: 12 · 2025: 11 · 2024: 16 · 2023: 18 · 2022: 24 · 2021: 30 · 2020: 46 · 2019: 28 · 2018: 34 · 2017: 48 · 2016: 54 · 2015: 50 · 2014: 51 · 2013: 64 · 2012: 62
- FWCI
- 27.15
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Licence
- Locations
- Nature Physics (publishedVersion)
- arXiv (Cornell University) (submittedVersion)
- CaltechAUTHORS (California Institute of Technology) (submittedVersion)
- arXiv (Cornell University)
- Funders
- National Science Foundation (0819860, 1006492)
- U.S. Department of Energy (DEFG0207ER46352, AC03-76SF00098, DE‐FG02‐, DEFG0205ER46200, FG02-07ER46352)
- Alfred P. Sloan Foundation
- Division of Materials Research (DMR-0819860, 1006492)
- Basic Energy Sciences (DE-FG-02-07ER46352, AC03-76SF00098, DE-FG-02-05ER46200, DE-FG02)
- Topics
- Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Topological Materials and Phenomena
- Physical Sciences › Physics and Astronomy › Condensed Matter Physics › Advanced Condensed Matter Physics
- Physical Sciences › Physics and Astronomy › Atomic and Molecular Physics, and Optics › Surface and Thin Film Phenomena
- Keywords
- topological insulators, Bi2Se3, surface states, iron doping, magnetic disturbances, Dirac fermions, time-reversal symmetry breaking, band hybridization, spin-momentum locking, electron dynamics, axions, monopoles
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