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Chiral solitons in a coupled double Peierls chain

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Science  09 Oct 2015:
Vol. 350, Issue 6257, pp. 182-185
DOI: 10.1126/science.aaa7055

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Handedness at the edge of a line

Topological insulators are characterized by conducting boundary states. For those existing as two-dimensional (2D) materials, the boundaries are lines, the edge currents are 1D, and their two spin components flow in opposite directions. To address whether this handedness also applies to the edge states of 1D topological systems, Cheon et al. deposited indium atoms on the surface of silicon, where the atoms formed wires consisting of double zigzag chains. The chains underwent distortions that caused topological edge states called solitons to appear under certain conditions. The solitons came in three flavors, two of which had a definite handedness.

Science, this issue p. 182

Abstract

Chiral edge states are the hallmark of two- and three-dimensional topological materials, but their one-dimensional (1D) analog has not yet been found. We report that the 1D topological edge states, solitons, of the charge density wave system of indium atomic wires self-assembled on a silicon surface have chirality. The system is described by a coupled double Peierls-dimerized atomic chain, where the interchain coupling induces dynamical sublattice symmetry breaking. This changes its topological symmetry from Embedded Image to Embedded Image and endows solitons with a chiral degree of freedom. Chiral solitons can produce quantized charge transport across the chain that is topologically protected and controllable by the soliton’s chirality. Individual right- and left-chiral solitons in indium wires are directly identified by scanning tunneling microscopy.

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