Sergio Garcia Magalhaes

This study systematically investigates the optoelectronic, mechanical, transport, and thermodynamic properties of Pb-free halide-based double perovskites (Rb ₂ LiIrX ₆ , where X[Formula: see text]Cl, Br) for energy conversion. Using density functional theory (DFT) within the full-potential linearized augmented plane-wave (FP-LAPW) framework implemented in the Wien2k code, structural optimizations were performed through the PBEsol generalized gradient approximation (GGA). Energy calculations yield values of [Formula: see text] eV (Cl) and [Formula: see text] eV (Br) for the cubic phase, thereby confirming its thermodynamic stability. Electronic band structures obtained with the modified Becke–Johnson (mBJ) potential reveal direct bandgaps of 2.25 eV (Cl) and 1.69 eV (Br); these findings are further validated by HSE06 hybrid functional calculations, establishing the semiconducting nature of both compositions. Mechanical robustness is confirmed through elastic constants and phonon dispersion analyses, demonstrating resilience against structural deformations. Optical properties display high absorption coefficients, higher static dielectric constants and low reflectivity, highlighting the material’s potential for photovoltaic and photodetector applications. Moreover, low lattice thermal conductivity and thermoelectric figure-of-merit (ZT) values approaching 1 suggest additional potential for thermoelectric energy harvesting. The high Debye temperatures and negative Gibbs free energies over a wide temperature range indicate the thermal stability of these compounds under operational conditions.

We obtain an exact analytic solution of the two-electron sector of the Underscreened Anderson Lattice Model (UALM), a minimal framework often invoked to capture the physics of partially Kondo-scree...

We predict new 2D MoX3 (X=Ga, In, Tl) monolayers using first-principles calculations. All MoX3 monolayers are structurally, dynamically, mechanically, and thermally stable, as evidenced by negative formation energies, satisfaction of the Born–Huang criteria, and the absence of imaginary phonon modes, with ab initio molecular dynamics further confirming stability at 300 K. The monolayers exhibit mixed covalent−ionic bonding between Mo and X atoms and display metallic behavior in all magnetic configurations. Magnetically, the MoX3 monolayers host diverse ground states arising from competing exchange interactions: MoGa3 stabilizes into an AFM3 state, MoIn3 adopts a ferromagnetic ground state, and MoTl3 favors AFM1 ordering. Exchange coupling parameters reveal strong sensitivity to X-site substitution, enabling tunable magnetic interactions. Remarkably large magnetocrystalline anisotropy energies (MAE) of 5.55 meV (MoGa3), 7.75 meV (MoIn3), and 40.90 meV (MoTl3) indicate robust perpendicular magnetic anisotropy in MoGa3 and MoIn3, while MoTl3 exhibits exceptionally strong in-plane anisotropy driven by enhanced Tl-induced spin–orbit coupling. Monte Carlo simulations predict ordering temperatures of 273.7, 172, and 223.2 K for MoGa3, MoIn3, and MoTl3, confirming near room-temperature antiferromagnetism in MoGa3 and MoTl3. The combination of high Néel temperatures, strong magnetic anisotropy, tunable exchange interactions, and intrinsic metallicity positions MoX3 monolayers as promising candidates for advanced spintronic applications. This study represents the first report of MoX3 monolayers incorporating group-13 elements (Ga, In, Tl), providing a versatile platform for designing functional 2D magnetic materials.

We examine the magnetic excitations of an Anderson lattice model with a V-shaped pseudogap arising from nodal hybridization. The model produces a V-shaped pseudogap in the electronic density of states near the Fermi energy. It lies close to an antiferromagnetic (AFM) quantum critical point and features low-dimensional Fermi surfaces, aligning with experimental observations of CeNiSn. The Anderson lattice model with nodal hybridization exhibits degenerate pairs of one-dimensional Fermi surfaces located at the center of the pseudogap. At energies slightly away from the Fermi energy, the constant-energy cuts evolve into small-area tori. We calculate both the static and dynamic magnetic susceptibilities, revealing distinct types of magnetic excitations. Analysis of the susceptibility indicates that the dynamic exponent at the quantum critical point is z = 1 , in contrast to the usual value z = 2 , found for metallic AFM quantum critical points. Since the calculated magnetic spectrum compares favorably with inelastic neutron scattering data on CeNiSn, the model may help resolve ongoing controversies in the interpretation of such experiments. Finally, we propose that the hypothesis of anisotropic hybridization can be tested via tunneling spectroscopy at sites adjacent to substitutional impurities.

In this study, we explore the effect of a single flat band in the electronic properties of a ferromagnetic two-dimensional Lieb lattice using the multiband Hubbard model with polarized carriers, spin-up and spin-down. We employ the self-consistent dynamical mean field theory and a Green functions cumulant expansion around the atomic limit to obtain the correlated densities of states while varying the intra- and interband interactions. Our findings demonstrate a renormalization of the correlated density of states in both the spin-up and spin-down carriers as we varied the intra- and interband interactions. We conclude that the presence of a flat band enables the system to maintain a metal state with itinerant ferromagnetism in the spin-up carrier.