arXiv subjects

Juan J. Palacios

Publications and source records attributed to Juan J. Palacios.

5 recordsLinked to original sources

arXiv2025

Excitonic optical absorption in strained monolayer CrSBr

Recently, the isolation of 2D magnetic materials has opened several avenues for possible new ap- plications in spintronics. Among these materials, CrSBr has sparked interest due to its relatively high Curie temperature, highly anisotropic lattice structure, and high structural stability. These properties ran along others shared by any atomically thin material such as its outstanding defor- mation capacity and a strong optical response dominated by excitonic effects. The combination of these properties provides a fairly uncharted playground where to explore the interplay between magnetism and optical excitations. Here, we focus our attention on the theoretical optical response of CrSBr under several distinct strain configurations, analyzing the resulting changes to both the excitonic peaks and overall shape of the diagonal components of the linear conductivity tensor.

cond-mat.mes-hall↗

arXiv2025

Magnetic order tuning of excitons in the magnetic semiconductor CrCl$_3$ through strain

Magnon-exciton coupling provides an unprecedented opportunity for the optical tunability of spin information and, viceversa, for the magnetic control of the optical response. Few-layered magnets are an ideal platform for the experimental study of this coupling, in part due to the strong excitonic character of the optical response in (quasi-)two dimensions. Here, we demonstrate a strong dependence of the excitonic oscillator strength on the magnetic order in a monolayer of chromium trichloride CrCl$_3$. Solving an effective Bethe-Salpeter equation, we evaluate the changes in the excitonic response as the magnetic order switches from the ferromagnetic state to the antiferromagnetic state when strain is applied. Our results reveal an abrupt change in the spatial localization of the excitons across the transition, which translates into a strong shift and a change of the oscillator strength of the excitonic peaks. This suggests the possibility of using strain as a binary switch of the optical response in this material.

cond-mat.mtrl-sci↗

arXiv2025

Quantum valley pseudospin controlled by strain

Valleytronics, as an alternative to traditional electronics or spintronics, is based on the encoding of quantum information in pseudospin valley quantum numbers, rather than in charge or spin states. A key ingredient is the (optical) manipulation of valley states before loss of coherence, which can be as fast as 100 femtoseconds. Previous works have shown the possibility of valley state manipulation using external fields. Here we propose uniaxial strain as a more flexible and robust scheme to manipulate the valley state through the breaking of the crystal symmetry and the concomitant lifting of the degeneracy of the 1s exciton energy. Our theory is corroborated by state-of-the-art numerical simulations in monolayer hBN and shows the possibility to control valley pseudospin at the attosecond time scale.

cond-mat.mes-hall↗

arXiv2025

Understanding Memristive Behavior: An Atomistic Study of the Influence of Grain Boundaries on Surface and Out-of-Plane Diffusion of Metallic Atoms

Atomic migration from metallic contacts, and subsequent filament formation, is recognised as a prevailing mechanism leading to resistive switching in memristors based on two-dimensional materials (2DMs). This study presents a detailed atomistic examination of the migration of different metal atoms across the grain boundaries (GBs) of 2DMs, employing Density Functional Theory in conjunction with Non-Equilibrium Green's Function transport simulations. Various types of metallic atoms, Au, Cu, Al, Ni, and Ag, are examined, focusing on their migration both in the out-of-plane direction through a MoS\textsubscript{2} layer and along the surface of the MoS\textsubscript{2} layer, pertinent to filament formation in vertical and lateral memristors, respectively. Different types of GBs usually present in MoS\textsubscript{2} are considered to assess their influence on the diffusion of metal atoms. The findings are compared with structures based on pristine MoS\textsubscript{2} and those with mono-sulfur vacancies, aiming to understand the key elements that affect the switching performance of memristors. Furthermore, transport simulations are carried out to evaluate the effects of GBs on both out-of-plane and in-plane electron conductance, providing valuable insights into the resistive switching ratio.

cond-mat.mtrl-sci↗

arXiv2010

Anomalous Transport and Possible Phase Transition in Palladium Nanojunctions

Many phenomena in condensed matter are thought to result from competition between different ordered phases. Palladium is a paramagnetic metal close to both ferromagnetism and superconductivity, and is therefore a potentially interesting material to consider. Nanoscale structuring of matter can modify relevant physical energy scales leading to effects such as locally modified magnetic interactions. We present transport measurements in electromigrated palladium break junction devices showing the emergence at low temperatures of anomalous sharp features in the differential conductance. These features appear symmetrically in applied bias and exhibit a temperature dependence of their characteristic voltages reminiscent of a mean field phase transition. The systematic variation of these voltages with zero-bias conductance, together with density functional theory calculations illustrating the relationship between the magnetization of Pd and atomic coordination, suggest that the features may result from the onset of spontaneous magnetization in the nanojunction electrodes. We propose that the characteristic conductance features are related to inelastic tunneling involving magnetic excitations.

cond-mat.mes-hall↗