arXiv subjects

Jhon W. González

Publications and source records attributed to Jhon W. González.

11 recordsLinked to original sources

arXiv2026

Chiral Magnons and Cycloidal Phonons in Altermagnetic CuF$_{2}$ Monolayer

Altermagnetism establishes momentum-dependent spin splitting through non-symmorphic crystal symmetries, yet whether these same symmetries simultaneously govern spin and lattice collective excitations remains open. Here we show, using first-principles calculations and linear spin-wave theory, that monolayer CuF$_2$ hosts both chirality-split magnons and cycloidal phonons controlled by the same $P2_1/c$ symmetry operations. The altermagnetic order drives strongly anisotropic magnon chirality via symmetric anisotropic exchange, with Dzyaloshinskii--Moriya interactions acting as a weak secondary modulation. Crucially, the phonon and magnon chiral responses are directionally complementary: cycloidal phonon angular momentum emerges precisely where magnon chirality is symmetry-suppressed, and vice versa. The magnon bands further carry quantized Chern numbers $C^M = \pm 2$, confirming non-trivial altermagnetic topology. These results establish monolayer CuF$_2$ as a platform where a single symmetry framework engineers magnonic, phononic, and topological responses, providing a direct connection between altermagnetism and spin-lattice chirality in two-dimensional materials.

cond-mat.mtrl-sci↗

arXiv2026

Synthetic Altermagnetism Beyond the Crystal Limit

Altermagnetic magnons in crystalline materials exhibit momentum-dependent splitting whose nodal structure and chiral character are governed by the point-group symmetry of the magnetic sublattice rotation. Here, we demonstrate the first synthetic realization of altermagnetic magnonics in a continuum platform composed of antiferromagnetically coupled ferromagnetic films with alternating in-plane exchange anisotropies, showing that the key signatures of altermagnetic magnonics emerge beyond the crystalline setting. Solving the linearized Landau-Lifshitz equation within a dipole-exchange framework, we show that this architecture reproduces the characteristic momentum-dependent splitting, nodal directions, and anisotropic isofrequency contours of A-type altermagnets. Long-range dipolar interactions qualitatively reconstruct this exchange-driven spectrum by lifting the nominal nodal degeneracy, hybridizing opposite-chirality modes, and producing a finite, thickness-dependent wave-vector splitting along directions that are nodal in the exchange-only limit. Extending the bilayer to finite multilayers reveals that synthetic altermagnetism undergoes a parity-dependent reconstruction that separates surface and bulk altermagnetic excitations. These results establish altermagnetic magnon phenomenology as an engineerable collective response of dipole-exchange multilayers beyond microscopic crystal symmetries.

cond-mat.other↗

arXiv2025

Hybrid d/p-wave altermagnetism in Ca$_{3}$Ru$_{2}$O$_{7}$ and strain-controlled spin splitting

The interplay of strong electronic correlations, sizable octahedral distortions, and pronounced spin-orbit coupling (SOC) makes perovskite oxides promising candidates for realizing altermagnetic phases. We study altermagnetic phases in Ca$_3$Ru$_2$O$_7$, a non-centrosymmetric layered perovskite whose ground state is a Kramers-degenerate antiferromagnet. We show that an alternative Néel-type spin arrangement hosts a P-2 d-wave altermagnetic state with orbital selectivity similar to Ca$_2$RuO$_4$. Including SOC generates a symmetry-allowed p-wave component and yields a hybrid d/p-wave altermagnetic order. We further demonstrate that biaxial strain tunes both magnetic stability and band splitting: compressive strain beyond 2 % favors the altermagnetic phase over the antiferromagnetic ground state, while tensile strain increases altermagnetic splittings by up to 9 %. To quantify these trends, we define an altermagnetic figure of merit and trace its strain dependence to changes in electronic localization and octahedral geometry in this polar metal.

cond-mat.mtrl-sci↗

arXiv2025

Optimizing Hubbard U parameters for Enhanced Description of Electronic and Magnetic Properties in CrI$_3$ Monolayers and Bilayers

The magnetic properties of CrI$_3$ monolayers, which were recently measured, have been investigated considering electronic repulsion and localization effects in Cr 3d orbitals. In this study, we propose a DFT approach using Hubbard U corrections to improve accuracy. We compare the valence density-of-states using the HSE06 hybrid functional and the DFT+U approach, which includes U parameters for both Cr 3d and I 5p orbitals. The results of our study indicate that the optimal values for U(Cr$_{3d}$) and U(I$_{5p}$) are 3.5 eV and 2.0 eV, respectively. This approach is further applied to improve calculations of electronic and magnetic properties in CrI$_3$ monolayers and, more importantly, in bilayers combined with van der Waals functionals. These refinements hold promise for further studies of complex CrI$_3$ nanostructures, and may also be of interest for other trihalide few-layer systems.

cond-mat.mes-hall↗

arXiv2022

V$_2$C-based lithium batteries: The influence of magnetic phase and Hubbard interaction

MXenes are a family of two-dimensional materials that could be attractive for use as electrodes in lithium batteries due to their high specific capacity. For this purpose, it is necessary to evaluate magnitudes such as the lithium adsorption energy and the magnitude of the open-circuit voltage for different lithium concentrations. In this paper, we show through first principles calculations that in a V$_2$C monolayer we must consider the high correlation between the electrons belonging to vanadium to obtain correct results of these quantities. We include this correlation employing the Hubbard coupling parameter obtained by a linear response method. We found that the system is antiferromagnetic and that the quantities studied depend on the magnetic phase considered. Indirectly, experimental results could validate the theoretical value of the theoretical Hubbard parameter.

cond-mat.mtrl-sci↗

arXiv2018

Highly anisotropic thermoelectric properties of carbon sulfide monolayers

Strain engineering applied to carbon monosulphide monolayers allows to control the bandgap, controlling electronic and thermoelectric responses. Herein, we study the semiconductor-metal phase transition of this layered material driven by strain control on the basis of first-principles calculations. We consider uniaxial and biaxial tensile strain and we find a highly anisotropic electronic and thermoelectonic responses depending on the direction of the applied strain. Our results indicate that strain-induced response could be an effective method to control the electronic response and the thermoelectric performance.

cond-mat.mes-hall↗

arXiv2018

Thermopower of Graphene Nanoribbons in the Pseudodiffusive Regime

Thermoelectric measurements for graphene ribbons are currently performed on samples that include atomic disorder via defects and irregular edges. In this work, we investigate the thermopower or Seebeck coefficient of graphene ribbons within the linear response theory and the Landauer formalism, and we consider the diffusive regime taken as a limit of the ribbon aspect ratio. We find that the thermopower and the electronic conductivity depend not only on the aspect ratio, but also on chemical potential and temperature, which are set here as key parameters. The obtained numerical results with temperature and doping are brought into contact with the thermoelectric measurements on disordered graphene ribbons with good agreement.

cond-mat.mes-hall↗

arXiv2018

Out-of-plane Enhanced Magnetic Anisotropy Energy in Ni$_{3}$Bz$_{3}$ molecule

Organometallic complexes formed by transition metals clusters and benzene molecules have already been synthesized, and in selected cases display magnetic properties controlled by external magnetic fields. We have studied Ni$_n$Bz$_n$ complexes made of nickel atoms surrounded by benzene molecules and here we focus specifically on the magnetic molecule Ni$_{3}$Bz$_{3}$. By means of calculations including relativistic spin-orbit terms, we show that this molecule reveals a large magnetic anisotropy energy of approximately 8 meV, found with the easy axis perpendicular to the metal atoms plane. Note that the matching bare Ni$_{3}$ cluster have similar magnetic anisotropy, however the easy axis is in-plane. Covering with benzene molecules is thus switching the easy axis from in-plane for Ni$_3$ to out-of-plane for Ni$_{3}$Bz$_{3}$. The large out-of-plane magnetic anisotropy of Ni$_{3}$Bz$_{3}$ suggests that this molecule could indeed be used as part in the design of molecular magnetic memories.

cond-mat.mtrl-sci↗

arXiv2017

Ultrashort Mn-Mn Bonds in Organometallic Complexes

Manganese metallocenes larger than the experimentally produced sandwiched MnBz$_2$ compound are studied using several density functional theory methods. First, we show that the lowest energy structures have Mn clusters surrounded by benzene molecules, in so-called rice-ball structures. We then find a strikingly short bond length of 1.8 Å between pairs of Mn atoms, accompanied by magnetism depletion. The ultrashort bond lengths are related to Bz molecules caging a pair of Mn atoms, leading to a Mn-Mn triple bond. This effect is also found when replacing benzenes by other molecules such as borazine or cyclopentadiene. The stability of the Mn-Mn bond for Mn$_2$Bz$_2$ is further investigated using dissociation energy curves. For each spin configuration, the energy versus distance plot shows different spin minima with barriers, which must be overcome to synthesize larger Mn-Bz complexes.

cond-mat.mtrl-sci↗

arXiv2017

Carbon Monosulfide Nanostructures: Chains Arrays, Monolayers, and Thin Films

Theoretical predictions have lead to the experimental synthesis of new low dimensional layered structures. Herein we show for the very first time that compounds of carbon monosulfide exhibit a great variety of layered nanostructures, such as chains arrays, monolayers, and thin films. We find that the chains arrays are the most stable because they are mainly dimensionality-driven by the $sp^2$ hybridization of sulfur and carbon orbitals. Furthermore, the chains arrays are direct gap semiconductors. In contrast to thin films, the monolayers are stable at room temperature with a semiconductor phase followed in energy by a metallic phase. Then, we achieve a semiconductor-to-metal phase transition in carbon sulfur monolayers, which can be driven by strain engineering controlling conductivity and carrier mobility.

cond-mat.mtrl-sci↗

arXiv2013

Electronic transport of folded graphene nanoribbons

We investigate the electronic transport properties of a folded graphene nanoribbon with monolayer nanoribbon contacts. We consider two possible foldings: either the nanoribbon can be folded onto itself in the shape of a hairpin with the nanoribbon leads at a $0^\circ$ angle, or the monolayer contacts have different directions, forming a $60^\circ$ angle. The system is described by a single $π$-band nearest-neighbor tight-binding Hamiltonian taking into account curvature effects. We have found that for the case of a nanoribbon folded over itself the conductance oscillates from almost zero and a finite value depending on the coupling between contacts, whereas in the $60^\circ$ angle folding the conductance is only slightly perturbed, allowing for the connection of graphene nanoelectronic components in a variety of geometries.

cond-mat.mes-hall↗