Dirac Cone with Helical Spin Polarization in Ultrathin<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>α</mml:mi></mml:math>-Sn(001) Films

Ohtsubo, Yoshiyuki; Fèvre, P. Le; Bertran, F.; Taleb‐Ibrahimi, A.

doi:10.1103/physrevlett.111.216401

Cited by 107 publications

(129 citation statements)

References 36 publications

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“…The left-hand panel shows the dispersion along the Γ-X direction (note that due to the dual domain nature of the surface reconstruction in our samples the X and Y points of the surface Brillouin zone (SBZ) can not be distinguished). At 0 eV binding energy we observe a single sharp feature that crosses E F , corresponding to the TSS reported recently 2,3 . In addition, we observe a weak background intensity caused by the projected bulk Γ + 8 band that also crosses E F , revealing a metallic behavior.…”

Section: Electronic Structuresupporting

confidence: 81%

“…The low-temperature α-phase of Sn has attracted considerable attention recently as a unique elemental threedimensional topologically non-trivial material [1][2][3][4][5][6][7] . Being a zero-gap semiconductor if unstrained, it can enter a Dirac semimetal or strong topological insulator (TI) phases under strain 6,7 .…”

Section: Introductionmentioning

confidence: 99%

“…Interestingly, the non-trivial topology and, hence, the topological surface state (TSS) in α-Sn exist independently of the strain owing to a robust band inversion between conduction and second valence bands, similar to HgTe 8 or some ternary Heusler compounds 9 . While the electronic structure of α-Sn has been reported in several experimental studies [2][3][4][5][6] , a detailed analysis of the TSS is still missing.…”

Section: Introductionmentioning

confidence: 99%

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Topological surface state of α−Sn on InSb(001) as studied by photoemission

et al. 2018

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We report on the electronic structure of the elemental topological semimetal α-Sn on InSb(001). High-resolution angle-resolved photoemission data allow to observe the topological surface state (TSS) that is degenerate with the bulk band structure and show that the former is unaffected by different surface reconstructions. An unintentional p-type doping of the as-grown films was compensated by deposition of potassium or tellurium after the growth, thereby shifting the Dirac point of the surface state below the Fermi level. We show that, while having the potential to break time-reversal symmetry, iron impurities with a coverage of up to 0.25 monolayers do not have any further impact on the surface state beyond that of K or Te. Furthermore, we have measured the spin-momentum locking of electrons from the TSS by means of spin-resolved photoemission. Our results show that the spin vector lies fully in-plane, but it also has a finite radial component. Finally, we analyze the decay of photoholes introduced in the photoemission process, and by this gain insight into the many-body interactions in the system. Surprisingly, we extract quasiparticle lifetimes comparable to other topological materials where the TSS is located within a bulk band gap. We argue that the main decay of photoholes is caused by intraband scattering, while scattering into bulk states is suppressed due to different orbital symmetries of bulk and surface states.

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Section: Electronic Structuresupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Topological surface state of α−Sn on InSb(001) as studied by photoemission

et al. 2018

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“…Liang Fu et al theoretically proposed that such an insulator phase was a strong 3D topological insulator [18]. Two recent experimental studies demonstrated the existence of topological surface states in the valence band regions of -Sn films grown on InSb(001), but no experimental evidence of the strain-induced gap [19,20].…”

mentioning

confidence: 99%

“…Fig. 1 [19] or Bi [20] into Sn films to help films grow smoothly, no such impurity atoms were introduced in our thin film samples yet they were of high-quality. The strain in the 30-BL film was measured by X-ray diffraction using the !…”

mentioning

confidence: 99%

Elemental Topological Dirac Semimetal: α -Sn on InSb(111)

et al. 2017

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Three-dimensional (3D) topological Dirac semimetals (TDSs) are rare but important as a versatile platform for exploring exotic electronic properties and topological phase transitions. A quintessential feature of TDSs is 3D Dirac fermions associated with bulk electronic states near the Fermi level. Using angle-resolved photoemission spectroscopy (ARPES), we have observed such bulk Dirac cones in epitaxially-grown 𝛼-Sn films on InSb(111), the first such TDS system realized in an elemental form. First-principles calculations confirm that epitaxial strain is key to the formation of the TDS phase. A phase diagram is established that connects the 3D TDS phase through a singular point of a zero-gap semimetal phase to a topological insulator (TI) phase. The nature of the Dirac cone crosses over from 3D to 2D as the film thickness is reduced.

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Thermal Stability Enhancement in Epitaxial Alpha Tin Films by Strain Engineering

et al. 2019

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Exploring new topological materials with large topological nontrivial bandgaps and simple composition is attractive for both theoretical investigation and experimental realization. Recently, alpha tin (α-Sn) has been predicted to be such a candidate, and it can be tuned to be either a topological insulator or a Dirac semimetal by applying appropriate strain. However, freestanding α-Sn is only stable below 13.2 C. Herein, a series of high-quality α-Sn films with different thicknesses are successfully grown on InSb substrates by molecular beam epitaxy (MBE). Confirmed by both X-ray diffraction (XRD) and reciprocal space mapping (RSM), all the films remain fully strained up to 400 nm, proving the strain effect from the substrate. Remarkably, the single-crystalline α phase can persist up to 170 C for the 20 nm thick sample. The critical temperature where the α phase disappears decreases as the film thickness increases, showing that the thermal stabilization can be engineered by varying the α-Sn thickness. A plastic flow model considering work hardening is introduced to explain this dependence, assuming that the strain relaxation and the phase transition occur successively. This enhanced thermal stability is prerequisite for aforementioned roomtemperature characterization and practical application of this material system.The diamond-structured allotrope of tin (alpha tin [α-Sn]), also known as gray tin, has attracted increasing research interest recently for its topological characters when the cubic symmetry is broken. [1][2][3][4][5][6] The advantages of this material are attributed to its simple structure and large tunable nontrivial bandgap. [2][3][4][5][6][7][8][9][10][11][12]

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Dirac Cone with Helical Spin Polarization in Ultrathinα-Sn(001) Films

Cited by 107 publications

References 36 publications

Topological surface state of α−Sn on InSb(001) as studied by photoemission

Topological surface state of α−Sn on InSb(001) as studied by photoemission

Elemental Topological Dirac Semimetal: α -Sn on InSb(111)

Thermal Stability Enhancement in Epitaxial Alpha Tin Films by Strain Engineering

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