arXiv subjects

Hugo Ascolani

Publications and source records attributed to Hugo Ascolani.

2 recordsLinked to original sources

arXiv2026

Spin polarization enhancement in a single-layer Bi(1-x)Sb(x) alloy on Ag(111) via isovalent substitution

Co-adsorption of Bi and Sb on Ag(111) at room temperature yields a single-layer Bi(1-x)Sb(x) alloy with a rectangular 3xsqrt(3) structure containing four atoms per unit cell (2/3 ML total coverage) and lacking long-range chemical order. We present an electronic structure study of this system combining angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations. To investigate the effect of inversion symmetry breaking induced by substituting a heavier atom (Bi) with a lighter isoelectronic one (Sb) within a fixed crystallographic framework, we focused on a Bi-rich composition. ARPES measurements reveal four surface-state bands, in good agreement with DFT calculations based on a rectangular four-atom overlayer unit cell. DFT calculations further show that Sb incorporation induces both in-plane and out-of-plane asymmetries in the electronic potential, leading to sizable spin splitting and spin polarization of the overlayer bands. Although these effects are partially reduced by interaction with the substrate, they remain significant. Our work illustrates, through a concrete model system, a general principle: incorporating a lighter isovalent element can significantly enhance spin polarization, potentially offering a useful design guideline for understanding and engineering Rashba-related systems.

cond-mat.mtrl-sci↗

arXiv2024

Single-layer of Bi$_{1-x}$Sb$_x$ grown on Ag(111)

In this work, we report the growth of a single mixed Bi$_{1-x}$Sb$_x$ layer, with diverse stoichiometries, on a Ag(111) substrate. The atomic geometry has been thoroughly investigated by low energy electron diffraction, scanning tunneling microscopy, and X-ray photoelectron spectroscopy experiments, as well as calculations based on density functional theory (DFT). We first determined that both pure systems (Bi/Ag(111) and Sb/Ag(111)) show similar behaviors: they form surface alloys with ($\sqrt{3}\times\sqrt{3}$)R30$^\circ$ periodicity for coverages lower than 1/3 ML, and undergo a dealloying transition for higher coverages up to 2/3 ML. We then established a simple preparation procedure to obtain a mixed Bi-Sb overlayer on Ag(111): it is essential to start with a surface completely covered by either of the two pure surface alloys and then deposit the other element on it. The energetics derived from DFT calculations provide insight into the systems preference towards the formation of this phase, and also predict a pathway to the formation of Bi-rich non-alloyed phases. The obtained mixed Bi-Sb phase has a lateral atomic arrangement very similar to the one in the non-alloyed phase observed for Sb on Ag(111), with Sb and Bi atoms distributed disorderly, and presents a significant vertical corrugation, promising considerable Rashba effects.

cond-mat.mtrl-sci↗