Francisco Sánchez-Ochoa

arXiv2024

Kekulé distortions in graphene on cadmium sulfide

The deposition of a two-dimensional material on the surface of a three-dimensional crystal can generate superlattices with electronic properties modified through the proximity spin-orbit effect. In this study, we found that Kekulé graphene superlattices are obtained by placing graphene on Cd-terminated (001)-(1$\times$1) cadmium sulfide (CdS) surface. From an effective model of Kekulé superlattices, which is corroborated by Density Functional Theory (DFT) calculations, we identified that the puckered surfqace of CdS modifies the on-site energies (staggered potential) and C-C bonds, giving rise to two possible $\sqrt{3} \times \sqrt{3}$ hexagonal superlattices, which are known as Kekulé-O graphene and Kekulé-Y with a quadratic band crossing point. Both Kekulé superlattices present spin-orbit coupling due to the interaction of graphene with the CdS surface. To guide the experimental realization of Kekulé superlattices based on graphene/CdS heterostructures, we simulate electron diffraction patterns, as well as images from High-Resolution Transmission Electron Microscopy (HRTEM), and Scanning Transmission Electron Microscopy in the mode of High Angle Annular Dark Field (STEM-HAADF).

cond-mat.mtrl-sci↗

arXiv2023

Atomically thin current pathways in graphene through Kekulé-O engineering

We demonstrate that the current flow in graphene can be guided on atomically thin current pathways by means of the engineering of Kekulé-O distortions. A grain boundary in these distortions separates the system into topological distinct regions and induces a ballistic domain-wall state. The state does not depend on the precise orientation of the grain boundary with respect to the graphene sublattice and therefore, permits to guide the current on arbitrary paths through the system. As the state is gapped, the current flow can be switched by electrostatic gates. Our findings can be explained by a generalization of the Jackiw-Rebbi model, where the electrons behave in one region of the system as fermions with an effective complex mass, making the device not only promising for technological applications but also a test-ground for concepts from high-energy physics. An atomic model supported by DFT calculations demonstrates that the proposed system can be realized by decorating graphene with Ti atoms.

cond-mat.mes-hall↗