Triggering a global density wave instability in graphene via local symmetry-breaking

Abstract

Two-dimensional quantum materials offer a robust platform for investigating the emergence of symmetry-broken ordered phases owing to the high tuneability of their electronic properties. For instance, the ability to create new electronic band structures in graphene through moiré superlattices from stacked and twisted structures has led to the discovery of several correlated and topological phases. Here we report an alternative method to induce an incipient symmetry-broken phase in graphene at the millimetre scale. We show that an extremely dilute concentration ($<0.3\%$) of surface adatoms can self-assemble and trigger the collapse of the graphene atomic lattice into a distinct Kekulé bond density wave phase, whereby the carbon C-C bond symmetry is broken globally. Using complementary momentum-resolved techniques such as angle-resolved photoemission spectroscopy (ARPES) and low-energy electron diffraction (LEED), we directly probe the presence of this density wave phase and confirm the opening of an energy gap at the Dirac point. We further show that this Kekulé density wave phase occurs for various Fermi surface sizes and shapes, suggesting that this lattice instability is driven by strong electron-lattice interactions. Our results demonstrate that dilute concentrations of self-assembled adsorbed atoms offer an attractive alternative route towards designing novel quantum phases in two-dimensional materials.

15 pages, 5 figures

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Cited by in corpus (10)

• Fermions in Boundary Conformal Field Theory : Crossing Symmetry and $\epsilon$-Expansion
• Observation of Kekulé vortices induced in graphene by hydrogen adatoms
• Twistronics of Kekulé Graphene: Honeycomb and Kagome Flat Bands
• Kekulé Induced Valley Birefringence and Skew Scattering in Graphene
• Bootstrapped Dimensional Crossover of a Spin Density Wave
• Intercalated structures formed by platinum on epitaxial graphene on SiC(0001)
• Defects in Graphene : A Topological Description
• Kekulé valence bond order in the honeycomb lattice optical Su-Schrieffer-Heeger Model and its relevance to Graphene
• Multipolar spin liquid in an exactly solvable model for $j_{\mathrm{eff}}=\frac{3}{2}$ moments
• Band structure and optical response of Kekulé-modulated $\alpha -{\mathcal{T}}_3$ model