Observation of Gapped Dirac Cones in a Two-Dimensional Su-Schrieffer-Heeger Lattice

Abstract

The Su-Schrieffer-Heeger (SSH) model in a two-dimensional rectangular lattice features gapless or gapped Dirac cones with topological edge states along specific peripheries. While such a simple model has been recently realized in photonic/acoustic lattices and electric circuits, its material realization in condensed matter systems is still lacking. Here, we study the atomic and electronic structure of a rectangular Si lattice on Ag(001) by angle-resolved photoemission spectroscopy and theoretical calculations. We demonstrate that the Si lattice hosts gapped Dirac cones at the Brillouin zone corners. Our tight-binding analysis reveals that the Dirac bands can be described by a 2D SSH model with anisotropic polarizations. The gap of the Dirac cone is driven by alternative hopping amplitudes in one direction and staggered potential energies in the other one and hosts topological edge states. Our results establish an ideal platform to explore the rich physical properties of the 2D SSH model.

Accepted for publication in Nature Communications

References in corpus (11)

• The electronic properties of graphene
• Chiral tunneling and the Klein paradox in graphene
• Dirac materials
• Visualization of higher-order topological insulating phases in two-dimensional dielectric photonic crystals
• Dirac Cones and Minigaps for Graphene on Ir(111)
• Direct observation of corner states in second-order topological photonic crystal slabs
• First direct observation of Dirac fermions in graphite
• Novel Topological Phase with Zero Berry Curvature
• The Rare Two-Dimensional Materials with Dirac Cones
• Superstructure-induced splitting of Dirac cones in silicene
• Experimental realization of two-dimensional weak topological insulators