Justin William Wells

Atomic-scale elucidation of phase transition pathways in two-dimensional (2D) materials is practically necessary for achieving desired architectures in next-generation devices, yet it remains hindered by insufficient understanding of defect-mediated kinetics. Here, we study the behavior of Se defects in mediating phase transitions in single-layer (SL) VSe₂ grown on Au(111), achieved through controlled thermal annealing and selenium (Se) replenishment. Using scanning tunneling microscopy (STM) and angle-resolved photoemission spectroscopy (ARPES), we find that the initial SL VSe₂ is a 1T phase featuring a substrate-induced moiré superstructure and that several annealing stages lead to two defective, Se-poor phases with an increased in-plane lattice constant. Density functional theory (DFT) calculations, which align closely with experimental findings, provide insights into the atomic structures of the defective V selenide compounds. Analysis of the calculated phase transition pathway reveals that the formation of Se defects is directly correlated with the annealing temperature, and the density of Se defects plays an important role in stabilizing the 2H phase in the streaked domain and modulating the phase transition. This study highlights the potential of properly controlling the density of Se defects in VSe₂ to manipulate the ratio of different phases within streaked domains, enabling tunable phase-engineered 2D van der Waals structures.

Sb is topologically non-trivial and semi-metallic, but differs from many TSMs because of its continuous band gap. By measuring its (112) surface using angle- and spin-resolved photoemission spectroscopy, Sb(112) was shown to have 1D spin-polarised surface states resembling those on vicinal Bi surfaces and many TIs and TSMs. The shape and spin-polarisation of the measured features and the calculated bands agreed. However, the measured features had a slightly steeper energy dispersion and different Fermi-momenta than the calculated bands. Both theoretical and experimental methods were necessary when determining the topology of Sb(112). The presence of projected bulk states near the Fermi-level and varying surface localisation of the electronic states meant it was challenging to deduce the topology of Sb(112) from the number of bands crossing the Fermi-level or a continuous contour in the bulk band gap. Ultimately, the calculations and measurements suggest that there are topological surface states on the Sb(112) surface.

In the Comment by Goletti [], concerns are raised regarding the interpretation of our experimental findings, as well as the application of basic ground-state density functional theory (DFT) models pertaining to the C ( 111 ) − ( 2 × 1 ) surface presented in our earlier publication [Reed , ]. These concerns are addressed and our interpretation of the results is ultimately reconfirmed. We present further analysis of the original data and introduce new measurements on previously unreported regions of the surface reconstructed ( 2 × 1 ) Brillouin zone, aiding in the evaluation of the dispersion relation at other high-symmetry points. We gain insights relating to the current use of DFT calculations that include many-body theories when relating to the occupied electronic structure of this surface as measured by angle-resolved photoelectron spectroscopy.

Most Rashba spin splitting experimentally studied so far has ideal lattice with inversion symmetry broken, which limits the possibility to minimize the presence of spin-degenerate carriers near the Fermi level. Here, we report a novel 2D Au₂Sb surface alloy decorated with periodic structural defects that exhibits modulation on the Rashba spin-orbit coupling band. Spin- and angle-resolved photoemission spectroscopy reveals a Rashba spin-split band with antiparallel spin polarization, significantly broadened compared to the Au₂Sn surface alloy. From the good agreement between the experimental results and DFT calculations, we identify that the broadening of the Rashba bands comes from variations in Sb atom corrugation induced by the periodic three-pointed star-shaped defects. These periodic defects can shift the energy position of the Rashba bands without breaking the in-plane rotational and mirror symmetries. Our findings highlight the potential to tune spin-dependent properties in 2D materials for spintronic applications.

We report energy renormalizations from electron-phonon and electron-magnon interactions in spin minority surface resonances on Ni(111). The different interactions are identified, disentangled, and quantified from the characteristic signatures they provide to the complex self-energy and the largely different binding energies at which they occur. The observed electron-magnon interactions exhibit a strong dependence on momentum and energy band position in the bulk Brillouin zone. In contrast, electron-phonon interactions from the same bands appear to be relatively momentum- and symmetry-independent. Additionally, a moderately strong ($\lambda>0.5$) electron-phonon interaction is distinguished from a near-parabolic spin majority band not crossing the Fermi level.

Understanding the collective behavior of the quasiparticles in solid-state systems underpins the field of non-volatile electronics, including the opportunity to control many-body effects for well-desired physical phenomena and their applications. Hexagonal boron nitride (hBN) is a wide energy bandgap semiconductor, showing immense potential as a platform for low-dimensional device heterostructures. It is an inert dielectric used for gated devices, having a negligible orbital hybridization when placed in contact with other systems. Despite its inertness, we discover a large electron mass enhancement in few-layer hBN affecting the lifetime of the $π$-band states. We show that the renormalization is phonon-mediated and consistent with both single- and multiple-phonon scattering events. Our findings thus unveil a so-far unknown many-body state in a wide-bandgap insulator, having important implications for devices using hBN as one of their building blocks.