In-Plane Chirality Control of a Charge Density Wave by Means of Shear Stress.

The transition metal dichalcogenide 1T-TaS exhibits a Charge Density Wave (CDW) with in-plane chirality. Due to the rich phase diagram, the Ferro-Rotational Order (FRO) can be tuned by external stimuli. The FRO is studied by Angle-Resolved Photoelectron Spectroscopy (ARPES), Raman spectroscopy, and Selected Area Electron Diffraction (SAED).

Temperature Induced, Reversible Switching of Ferro-Rotational Order Coupled to Superlattice Commensuralibity.

High-quality 1T-TaS crystals are investigated by angle-resolved photoelectron spectroscopy, Raman spectroscopy, and low-energy electron diffraction. The Ferro-Rotational Order (FRO) of the charge density wave switches configuration at the transition between the commensurate and the nearly commensurate phase. This process requires samples without built-in or externally induced strain.

Direct Quantifying Charge Transfer by 4D-STEM: A Study on Perfect and Defective Hexagonal Boron Nitride.

Four-dimensional scanning transmission electron microscopy (4D-STEM) offers an attractive approach to simultaneously obtain precise structural determinations and capture details of local electric fields and charge densities. However, accurately extracting quantitative data at the atomic scale poses challenges, primarily due to probe propagation and size-related effects, which may even lead to misinterpretations of qualitative effects. In this study, we present a comprehensive analysis of electric fields and charge densities in both pristine and defective h-BN flakes.

On-Surface Synthesis and Evolution of Self-Assembled Poly(-phenylene) Chains on Ag(111): A Joint Experimental and Theoretical Study.

The growth of controlled 1D carbon-based nanostructures on metal surfaces is a multistep process whose path, activation energies, and intermediate metastable states strongly depend on the employed substrate. Whereas this process has been extensively studied on gold, less work has been dedicated to silver surfaces, which have a rather different catalytic activity. In this work, we present an experimental and theoretical investigation of the growth of poly--phenylene (PPP) chains and subsequent narrow graphene ribbons starting from 4,4″-dibromo--terphenyl molecular precursors deposited at the silver surface.

Cathodoluminescence excitation spectroscopy: Nanoscale imaging of excitation pathways.

Following optical excitations' life span from creation to decay into photons is crucial in understanding materials photophysics. Macroscopically, this is studied using optical techniques, such as photoluminescence excitation spectroscopy. However, excitation and emission pathways can vary at nanometer scales, preventing direct access, as no characterization technique has the relevant spatial, spectral, and time resolution.