By a News Reporter-Staff News Editor at Science Letter -- Research findings on Science are discussed in a new report. According to news reporting out of Ibaraki, Japan, by NewsRx editors, research stated, "Low-dimensional electronic systems have traditionally been obtained by electrostatically confining electrons, either in heterostructures or in intrinsically nanoscale materials such as single molecules, nanowires and graphene. Recently, a new method has emerged with the recognition that symmetry-protected topological (SPT) phases(1,2), which occur in systems with an energy gap to quasiparticle excitations (such as insulators or superconductors), can host robust surface states that remain gapless as long as the relevant global symmetry remains unbroken."
Our news journalists obtained a quote from the research from National Institute for Materials Science, "The nature of the charge carriers in SPT surface states is intimately tied to the symmetry of the bulk, resulting in one- and two-dimensional electronic systems with novel properties. For example, time reversal symmetry endows the massless charge carriers on the surface of a three-dimensional topological insulator with helicity, fixing the orientation of their spin relative to their momentum(3,4). Weakly breaking this symmetry generates a gap on the surface(5), resulting in charge carriers with finite effective mass and exotic spin textures(6). Analogous manipulations have yet to be demonstrated in two-dimensional topological insulators, where the primary example of a SPT phase is the quantum spin Hall state(7,8). Here we demonstrate experimentally that charge-neutral monolayer graphene has a quantum spin Hall state(9,10) when it is subjected to a very large magnetic field angled with respect to the graphene plane. In contrast to time-reversal-symmetric systems(7), this state is protected by a symmetry of planar spin rotations that emerges as electron spins in a half-filled Landau level are polarized by the large magnetic field. The properties of the resulting helical edge states can be modulated by balancing the applied field against an intrinsic antiferromagnetic instability(11-13), which tends to spontaneously break the spin-rotation symmetry."
According to the news editors, the research concluded: "In the resulting canted antiferromagnetic state, we observe transport signatures of gapped edge states, which constitute a new kind of one- dimensional electronic system with a tunable bandgap and an associated spin texture(14)."
For more information on this research see: Tunable symmetry breaking and helical edge transport in a graphene quantum spin Hall state. Nature, 2014;505(7484):528-532,138-147. Nature can be contacted at: Nature Publishing Group, Macmillan Building, 4 Crinan St, London N1 9XW, England. (Nature Publishing Group - www.nature.com/; Nature - www.nature.com/nature/)
Our news journalists report that additional information may be obtained by contacting A.F. Young, Natl Inst Mat Sci, Adv Mat Lab, Tsukuba, Ibaraki 3050044, Japan. Additional authors for this research include J.D. Sanchez-Yamagishi, B. Hunt, S.H. Choi, K. Watanabe, T. Taniguchi, R.C. Ashoori and P. Jarillo-Herrero (see also Science).
Keywords for this news article include: Asia, Japan, Ibaraki, Science
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