L. C. Gomes | Searcharxiv

arXiv2025

The Moon as a possible source for Earth's co-orbital bodies

There is a growing number of Earth's co-orbital bodies being discovered. At least five of them are known to be temporarily in quasi-satellite orbits. One of those, 469219 Kamo'oalewa, was identified as possibly having the same composition as the Moon. We explore the conditions necessary for lunar ejecta to evolve into Earth's co-orbital bodies, with particular attention to the formation of quasi-satellite orbits. We systematically investigate the parameter space of ejection velocity and geographic launch location across the entire lunar surface. The study employs numerical simulations of the four-body problem (Sun-Earth-Moon-particle) with automated classification methodology for identifying all co-orbital states. Particles are ejected from randomly distributed points covering the entire lunar surface with velocities ranging from 1.0 to 2.6 times the Moon's escape velocity. Trajectories co-orbital to Earth are found to be a common outcome, with approximately 6.15% of all simulated particles evolving into Earth co-orbital motion and 1.92% specifically exhibiting quasi-satellite behavior. We identify an optimal ejection velocity (1.2 times escape velocity) for quasi-satellite production, yielding over 6% conversion efficiency at this specific velocity. The spatial distribution of successful ejections shows a strong preference for the equatorial regions of the trailing hemisphere. Collisions with Earth or the Moon occur for only 4% of the sample. Our results strengthen the plausibility of lunar origin for Earth's co-orbital bodies, including quasi-satellites like Kamo'oalewa and 2024 PT5. We identify both "prompt" and "delayed" co-orbital formation mechanisms, with a steady-state production regime that could explain the presence of lunar-derived objects in Earth's co-orbital regions despite the infrequent occurrence of major lunar impacts capable of launching meter-scale fragments.

astro-ph.EP↗

arXiv2015

Valleytronics in Tin (II) Sulfide

Tin (II) sulfide (SnS) is a layered mineral found in nature. In this paper, we study the two-dimensional form of this material using a combination of \emph{ab initio} calculation and $\mathbf{k}\cdot\mathbf{p}$ theory. In particular, we address the valley properties and the optical selection rules of 2D SnS. Our study reveals SnS as an extraordinary material for valleytronics, where pairs of equivalent valleys are placed along two perpendicular axes, can be selected exclusively with linear polarized light, and can be separated using non-local electrical measurements.

cond-mat.mes-hall↗

arXiv2012

Stability of extended defects on boron nitride and graphene monolayers: the role of chemical environment

We perform ab initio calculations that indicate that the relative stability of antiphase boundaries (APB) with armchair and zigzag chiralities in monolayer boron nitride (BN) is determined by the chemical potentials of the boron and nitrogen species in the synthesis process. In an N-rich environment, a zigzag APB with N-rich core is the most stable structure, while under B-rich or intrinsic growth conditions, an armchair APB with stoichiometric core is the most stable. This stability transition is shown to arise from a competition between homopolar-bond (B-B and N-N) and elastic energy costs in the core of the APBs. Moreover, in the presence of a carbon source we find that a carbon-doped zigzag APB becomes the most stable boundary near the N-rich limit. The electronic structure of the two types of APBs in BN is shown to be particularly distinct, with the zigzag APB depicting defect-like deep electronic bands in the band gap, while the armchair APB shows bulk-like shallow electronic bands.

cond-mat.mes-hall↗