Mapping the orbital wavefunction of the surface states in three-dimensional topological insulators

Cao, Yue; Waugh, Justin; Zhang, X. W.; Luo, Jun-Wei; Wang, Q.; Reber, T. J.; Mo, S.-K.; Xu, Zhijun; Yang, Alina; Schneeloch, John; Gu, Genda; Brahlek, Matthew; Bansal, Namrata; Oh, Seongshik; Zunger, Alex; Dessau, D. S.

doi:10.1038/nphys2685

Cited by 140 publications

(154 citation statements)

References 23 publications

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“…The contour is a circle at the high energy end, shrinks to a point at the Dirac point, and opens up at lower energies; this latter contour is strongly modulated in intensity and appears more like two spots. The modulation can be attributed to matrix element effects associated with the s-polarization geometry in our experiments [33]. The weak CB feature in Fig.…”

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confidence: 83%

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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confidence: 83%

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

et al. 2017

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“…2,12 We employ polarization dependent ARPES to confirm the orbital character determined by DFT. Applying symmetry arguments to the photoemission matrix element 25,26 in conjunction with dipole selection rules, allows us to extract the parity and atomic orbital composition of the electronic wavefunction. This is achieved by comparing the photoemission intensity when the perturbing electric field is even versus odd in the plane defined by the Poynting vector of the light and the sample normal.…”

Section: Resultsmentioning

confidence: 99%

Measurement of the atomic orbital composition of the near-fermi-level electronic states in the lanthanum monopnictides LaBi, LaSb, and LaAs

et al. 2018

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Recent debates in the literature over the relationship between topology and Extreme Magnetoresistance (XMR) have drawn attention to the Lanthanum Monopnictide family of binary compounds. Angle resolved photoemission spectroscopy (ARPES) is used to measure the electronic structure of the XMR topological semimetal candidates LaBi, LaSb, and LaAs. The orbital content of the near-E F states in LaBi and LaSb are extracted using varying photon polarizations and both dominant d and p bands are observed near X. The measured bulk bands are shifted in energy when compared to the results of Density Functional Calculations. This disagreement is minor in LaBi, but large in LaSb and LaAs. The measured bulk band structure of LaBi shows a clear band inversion and puts LaBi in the υ = 1 class of Topological Insulators (or semimetals), as predicted by calculations and consistent with the measured Dirac-like surface states. LaSb is on the verge of a band inversion with a less-clear case for any distinctly topological surface states and in disagreement with calculations. Lastly, these same bands in LaAs are clearly non-inverted implying its topological triviality and demonstrating a topological phase transition in the Lanthanum monopnictides. Using a wide range of photon energies the true bulk states are cleanly disentangled from the various types of surface states which are present. These surface states exist due to surface projections of bulk states in LaSb and for topological reasons in LaBi.

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“…The observation of the finite P x,z may, at first glance, be surprising because the spin-orbital texture locks the spin of the TSS electrons into y at (−k F , 0) [15,16]. Thus, the spin polarization effect in the photoelectrons cannot be explained by the spin-orbital textures alone but by photoemission matrix element effect [21,[25][26][27].…”

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confidence: 99%

“…The TSS forms spin-polarized Dirac-cone-like energy dispersion [9][10][11][12][13][14]. In particular, as a consequence of the strong SOC, different spins and orbitals are mixed in the TSS wavefunction, which generates a spin-orbital entangled texture [15][16][17]. Since the electric field of light couples to the orbitals, polarized light can, in princi-ple, selectively excite the fully spin-polarized electrons with either spin-up or spin-down from the spin-orbital entanglement.…”

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confidence: 99%

Coherent control over three-dimensional spin polarization for the spin-orbit coupled surface state of Bi2Se3

et al. 2016

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Interference of spin-up and spin-down eigenstates depicts spin rotation of electrons, which is a fundamental concept of quantum mechanics and accepts technological challenges for the electrical spin manipulation. Here, we visualize this coherent spin physics through laser spin-and angle-resolved photoemission spectroscopy on a spin-orbital entangled surface-state of a topological insulator. It is unambiguously revealed that the linearly polarized laser can simultaneously excite spin-up and spin-down states and these quantum spin-basis are coherently superposed in photoelectron states. The superposition and the resulting spin rotation is arbitrary manipulated by the direction of the laser field. Moreover, the full observation of the spin rotation displays the phase of the quantum states. This presents a new facet of laser-photoemission technique for investigation of quantum spin physics opening new possibilities in the field of quantum spintronic applications.PACS numbers: 73.20. At, Coherent manipulation of electron spin offers many potential applications in spintronic devices [1] and spinbased quantum information science [2,3]. The key is to take control over the superposition of spin-up and spindown states resulting in interference. Spin-orbit coupling (SOC) mediates electric field and electron spin; thus electric/optical control of spins may become possible. Up to now, the coherent spin manipulation through electric fields is demonstrated in a few systems, such as quantum qubits [3,4] and semiconductor-heterostructure interfaces [5]. Optical control of spins utilizing the superimposed states in diamond is also demonstrated [6]. In this Letter we introduce a great methodology which is capable of directly accessing this scheme in photoelectron spin, based on a combination of polarization-variable laser with spin-and angle-resolved photoemission spectroscopy (laser-SARPES).We use the technique for a well-understood model system, a spin-polarized surface state of a topological insulator (TI), Bi 2 Se 3 . The TI has been discovered as a new class of matter, which is characterized by a metallic topological surface-state (TSS) intersecting the bulk bandgap [7,8]. The TSS forms spin-polarized Dirac-cone-like energy dispersion [9][10][11][12][13][14]. In particular, as a consequence of the strong SOC, different spins and orbitals are mixed in the TSS wavefunction, which generates a spin-orbital entangled texture [15][16][17]. Since the electric field of light couples to the orbitals, polarized light can, in princi- * These two authors contributed equally. † kuroken224@issp.u-tokyo.ac.jp ‡ komori@issp.u-tokyo.ac.jp ple, selectively excite the fully spin-polarized electrons with either spin-up or spin-down from the spin-orbital entanglement. The spin-selective excitation in the TSS by polarized light was theoretically studied [18,19] and demonstrated in previous SARPES experiments [20][21][22][23]. The entangled spin-orbital texture of the TSS is therefore suitable for the coherent spin control as a novel source of spin...

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Mapping the orbital wavefunction of the surface states in three-dimensional topological insulators

Cited by 140 publications

References 23 publications

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

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

Measurement of the atomic orbital composition of the near-fermi-level electronic states in the lanthanum monopnictides LaBi, LaSb, and LaAs

Coherent control over three-dimensional spin polarization for the spin-orbit coupled surface state of Bi2Se3

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