Helical trilayer graphene (HTG) has emerged as a highly tunable moire quantum material that hosts strong electronic correlations and nontrivial band topology. However, the atomic-scale lattice structure and local electronic properties have remained largely unexplored. Here we present a comprehensive real-space study of HTG using a combination of scanning near-field optical microscopy and low-temperature scanning tun…
Grain boundaries fundamentally dictate the macroscopic properties of polycrystalline materials by breaking long-range symmetry. In ferroelectrics, these structural discontinuities are conventionally considered as detrimental features that induce depolarization fields and accumulate defects, thereby suppressing or pinning local polarization. Here, we demonstrate that the commensurability of grain boundaries inherentl…
Chuqiao Shi, Xinyan Li, Xing He, Kaiji Zhao, Jesse Schimpf, Akash Surampalli, Adan Mireles, Sergio Puebla, Yi Jiang, Ramamoorthy Ramesh, Xiaofeng Qian, Lane W. Martin, Andrew M. Rappe, Yimo Han
Floquet band engineering has been intensively studied for its potential to control material properties via laser driving. In particular, Floquet topological states have been measured on the surface of Bi$_2$Se$_3$. Nonetheless, the original prediction of Floquet topological bands in graphene remains unobserved, with works only measuring non-topological Floquet-Bloch states or indirect features. Here, we theoreticall…
Complex matter, often partly soft and pliable, is the generic form of material systems. We must therefore generally call on density functional theory (DFT) to first predict the atomic structure before we can use it to also characterize (expected) properties. A recent range-separated hybrid (RSH) van Waals density functional (vdW-DF), `vdW-DF2-ahbr' (abbreviated AHBR) [PRX 12, 041003 (2022)], shows promise as a high-…
In this work, the structural stability, and the electronic and magnetic properties of a novel CeN monolayer derived from the (111) surface of bulk rock salt CeN are investigated using first-principles calculations. Dimensional reduction produces substantial changes in the local atomic environment, decreasing the Ce-N coordination from sixfold in the bulk to threefold in the monolayer and shortening the Ce-N bond len…
Cation distribution plays a critical role in determining the properties of crystalline oxides. Understanding the chemical factors that govern cation distribution is therefore essential for the rational design of cation-ordered materials, particularly frustrated magnets in which structural disorder can strongly affect the magnetic ground state. Here, we investigate the origin and evolution of cation distribution in t…
The anisotropy of magnetic susceptibility (AMS) is a widely used tool to infer rock fabrics, yet quantitative interpretation is limited by sparse single-crystal magnetic properties for rock-forming minerals and by the difficulty of separating intrinsic diamagnetism from impurity-related magnetism. Here we use density-functional theory (DFT) combined with perturbation theory to compute the diamagnetic susceptibility…
Flat-band electronic states can be highly sensitive to chemical perturbations, offering opportunities to access a broader range of electronic behaviors beyond that of parent materials. Here, we report the discovery of a new series of compounds, Mo4TGa16Ge (T = Co, Rh, or Ir), derived from the strongly correlated flat-band superconductor, Mo4PtGa17, via nominally preserving the total valence electron counts. All thre…
