Marek Kopciuszynski

Reflection High-Energy Electron Diffraction (RHEED) is a widely used surface-science technique for real-time monitoring of crystal-surface quality, surface reconstructions or ultrathin film growth. Despite its power, RHEED often produces complex diffraction patterns arising from geometric constraints, making interpretation challenging. Here, we present xRHEED, a Python package that provides a flexible and extensible framework for RHEED image analysis, including diffraction profile extraction, kinematic simulations based on Ewald-sphere construction, and transformation of RHEED images into scattering-vector space. These capabilities enable sophisticated, reproducible analysis workflows and integrates naturally with the scientific Python ecosystem.

Scanning photoemission microscopy (SPEM) and angle-resolved photoemission spectroscopy (ARPES) are used to investigate the electronic structure of Cu 0.33 TiSe 2 across the charge density wave (CDW) transition. The electronic structure is found to be largely homogeneous in the normal state above the CDW transition. The ARPES measurements using a submicron beam size reveal a large electronlike pocket due to the Ti band at the M point while the Se 4 p band at the Γ point is absent due to electron doping by the intercalated Cu. We have observed 3 × 3 Fermi surface reconstruction below the CDW transition, in which Ti 3 d bands are folded into a reconstructed BZ rotated by 30 ∘ , making the Γ and K points equivalent. The results demonstrate the presence of a 3 × 3 CDW phase in the electronic structure of heavily Cu-intercalated Cu 0.33 TiSe 2 . The findings reveal a platform for investigating the two-dimensional electronic phase in 1T- TiSe 2 chalcogenides, which exhibit a unique interplay between CDW, superconductivity, and excitonic/lattice instabilities.

Partially embedded Pb chains are synthesized on a vicinal Si(113) surface in a process of self-organization. The deposition of one monolayer-range amount of Pb orders the substrate over the macroscopic scale and results in extremely long monatomic chains reproducing Si lattice geometry, as demonstrated by reflection high-energy electron diffraction and scanning tunneling microscopy. Angle-resolved photoelectron spectroscopy reveals well-developed one-dimensional metallic bands. Ab initio density functional theory calculations fully support the experimental findings and predict partially embedded zigzag Pb chains with substantially spin-orbit-split one-dimensional electron bands. The present work is experimental evidence of a new type of one-dimensional structures in which one of two chains of atoms building the structure is embedded in the substrate.

Massless fermions forming fortune teller states in a surface layer of Si(110).