Welcome to Santos' Research
The Santos' Research Lab is a theoretical research group specialised in computational simulations and theoretical methods. Our team consists of researchers from a diverse background in condensed-matter physics and chemistry, materials science, computing, and information technologies. Our mission is to advance the field of theoretical modeling through our research and innovation.
Publications in Santos' Research Lab
Our lab has published multiple research papers in top-tier scientific journals. Our publications focus on various topics in theoretical modeling and computational simulations. We strive to contribute to the scientific community with our innovative research and findings. Some highlights are included below. The full publication list is available at Google Scholar.
Coexistence of Merons with Skyrmions in the Centrosymmetric Van Der Waals Ferromagnet Fe5–xGeTe2
Fe5–xGeTe2 is a centrosymmetric, layered van der Waals (vdW) ferromagnet that displays Curie temperatures Tc (270–330 K) that are within the useful range for spintronic applications. However, little is known about the interplay between its topological spin textures (e.g., merons, skyrmions) with technologically relevant transport properties such as the topological Hall effect (THE) or topological thermal transport. Here, via high-resolution Lorentz transmission electron microscopy, it is shown that merons and anti-meron pairs coexist with Néel skyrmions in Fe5–xGeTe2 over a wide range of temperatures and probe their effects on thermal and electrical transport. A THE is detected, even at room T, that senses merons at higher T's, as well as their coexistence with skyrmions as T is lowered, indicating an on-demand thermally driven formation of either type of spin texture. These results expose Fe5–xGeTe2 as a promising candidate for the development of applications in skyrmionics/meronics due to the interplay between distinct but coexisting topological magnetic textures and unconventional transport of charge/heat carriers. Journal cover.
Spin dynamics in van der Waals magnetic systems
The discovery of atomic monolayer magnetic materials has stimulated intense research activities in the two-dimensional (2D) van der Waals (vdW) materials community. The field is growing rapidly and there has been a large class of 2D vdW magnetic compounds with unique properties, which provides an ideal platform to study magnetism in the atomically thin limit. While the magnetic ground state has been extensively investigated, reliable characterization and control of spin dynamics play a crucial role in designing ultrafast spintronic devices. Ferromagnetic resonance (FMR) allows direct measurements of magnetic excitations, which provides insight into the key parameters of magnetic properties such as exchange interaction, magnetic anisotropy, gyromagnetic ratio, spin–orbit coupling, damping rate, and domain structure. In this review article, we present an overview of the essential progress in probing spin dynamics of 2D vdW magnets using FMR techniques. Given the dynamic nature of this field, we focus mainly on broadband FMR, optical FMR, and spin-torque FMR, and their applications in studying prototypical 2D vdW magnets. We conclude with the recent advances in laboratory- and synchrotron-based FMR techniques and their opportunities to broaden the horizon of research pathways into atomically thin magnets​. Issue cover.
Quantum Rescaling, Domain Metastability, and Hybrid Domain-Walls in 2D CrI3 Magnets
Higher-order exchange interactions and quantum effects are widely known to play an important role in describing the properties of low-dimensional magnetic compounds. Here, the recently discovered 2D van der Waals (vdW) CrI3 is identified as a quantum non-Heisenberg material with properties far beyond an Ising magnet as initially assumed. It is found that biquadratic exchange interactions are essential to quantitatively describe the magnetism of CrI3 but quantum rescaling corrections are required to reproduce its thermal properties. The quantum nature of the heat bath represented by discrete electron–spin and phonon–spin scattering processes induces the formation of spin fluctuations in the low-temperature regime. These fluctuations induce the formation of metastable magnetic domains evolving into a single macroscopic magnetization or even a monodomain over surface areas of a few micrometers. Such domains display hybrid characteristics of Néel and Bloch types with a narrow domain wall width in the range of 3–5 nm. Similar behavior is expected for the majority of 2D vdW magnets where higher-order exchange interactions are appreciable. Journal cover.