Observation of Unconventional Quantum Spin Textures in Topological Insulators

Abstract

A topologically ordered material is characterized by a rare quantum organization of electrons that evades the conventional spontaneously broken symmetry-based classification of condensed matter. Exotic spin-transport phenomena, such as the dissipationless quantum spin Hall effect, have been speculated to originate from a topological order whose identification requires a spin-sensitive measurement, which does not exist to this date in any system. Using Mott polarimetry, we probed the spin degrees of freedom and demonstrated that topological quantum numbers are completely determined from spin texture-imaging measurements. Applying this method to Sb and Bi(1-x)Sb(x), we identified the origin of its topological order and unusual chiral properties. These results taken together constitute the first observation of surface electrons collectively carrying a topological quantum Berry's phase and definite spin chirality, which are the key electronic properties component for realizing topological quantum computing bits with intrinsic spin Hall-like topological phenomena.

Topological Insulator Nanowires and Nanoribbons

“…Angleresolved photoemission spectroscopy (ARPES) measurements on bulk single crystals of BixSb1-x, Bi2Se3, and Bi2Te3 have verified the existence of the 3D TI phase. [3][4][5][6][7] In particular, the surface states of Bi2Se3 forms a single Dirac cone inside a large bulk band gap of 0.3 eV, thus being suggested as the reference material for the 3D TIs. 2,4,8 The unique properties of the Bi2Se3 TI may pave the way for dissipationless quantum electronics and room temperature spintronics applications.…”

“…[3][4][5][6][7] Single crystalline nanostructure, on the other hand, offers an attractive alternative system to study the surface states, for example, by transport measurements or surface scanning techniques. As the sample * Corresponding author.…”

“…1 To date, the surface properties of the 3D TIs have been mainly investigated by ARPES measurements on the cleaved surface of bulk crystals. [3][4][5][6][7] Single crystalline nanostructure, on the other hand, offers an attractive alternative system to study the surface states, for example, by transport measurements or surface scanning techniques. As the sample size shrinks, the contribution of surface states to electrical and optical properties is enhanced due to the increase of the surface-to-volume ratio.…”

Spin-resolved photoemission study of epitaxially grown MoSe2and WSe2thin films

“…The additional information on spin polarization can be obtained through spin-resolved ARPES (SARPES) [31,32,33] as has been shown for topological surface states in topological insulators [34,35,36]. There has been only a few SARPES studies on MX 2 [37,38,39] despite the large interest on the material class, mainly due to the difficulty in preparing large area samples suitable for measurements in ultra-high vacuum environment, as current SARPES setups at the synchrotron source are bound to large beam spot size to allow maximum photon flux.…”

Magneto-transport behaviour of Bi2Se3−xTex: role of disorder

“…Following the initial elegant experiments using angle resolved photoemission spectroscopy (ARPES) [5][6][7][8] and scanning tunnelling microscopy (STM) [9] that provided an unambiguous evidence for the presence of Dirac dispersed 2D states, the current interest in this field has shifted to exploring the novel transport properties of 2D surface states (SS).…”