Origin of competing charge density waves in kagome metal ScVSn.

Understanding competing charge density wave (CDW) orders in the bilayer kagome metal ScVSn remains challenging. Experimentally, upon cooling, short-range order with wave vector forms, which is subsequently suppressed by the condensation of long-range CDW order at lower temperature. Theoretically, however, the q CDW is predicted as the ground state, leaving the CDW mechanism elusive.

Depth-Resolved X-Ray Photoelectron Spectroscopy Evidence of Intrinsic Polar States in HfO-Based Ferroelectrics.

The discovery of ferroelectricity in nanoscale hafnia-based oxide films has spurred interest in understanding their emergent properties. Investigation focuses on the size-dependent polarization behavior, which is sensitive to content and movement of oxygen vacancies. Though polarization switching and electrochemical reactions is shown to co-occur, their relationship remains unclear.

Lattice Dynamics of Quasi-2D Perovskites from First Principles.

We present the vibrational properties and phonon dispersion for quasi-2D hybrid organic-inorganic perovskites (BA)CsPbI, (HA)CsPbI, (BA)(MA)PbI, and (HA)(MA)PbI calculated from first principles. Given the highly complex nature of these compounds, we first perform careful benchmarking and convergence testing to identify suitable parameters to describe their structural features and vibrational properties. We find that the inclusion of van der Waals corrections on top of generalized gradient approximation (GGA) exchange-correlation functionals provides the best agreement for the equilibrium structure relative to experimental data.

Distinguishing Quasiparticle-Phonon Interactions by Ultrahigh-Resolution Lifetime Measurements.

We present a determination of quasiparticle-phonon interaction strengths at surfaces through measurements of phonon spectra with ultrahigh energy resolution. The lifetimes of low energy surface phonons on a pristine Ru(0001) surface were determined over a wide range of temperatures and an analysis of the temperature dependence enables us to attribute separate contributions from electron-phonon interactions, phonon-phonon interactions, and defect-phonon interactions. Strong electron-phonon interactions are evident at all temperatures and we show they dominate over phonon-phonon interactions below 400 K.