Interplay between spin proximity effect and charge-dependent exciton dynamics in MoSe2/CrBr3 van der Waals heterostructures.

Semiconducting ferromagnet-nonmagnet interfaces in van der Waals heterostructures present a unique opportunity to investigate magnetic proximity interactions dependent upon a multitude of phenomena including valley and layer pseudospins, moiré periodicity, or exceptionally strong Coulomb binding. Here, we report a charge-state dependency of the magnetic proximity effects between MoSe2 and CrBr3 in photoluminescence, whereby the valley polarization of the MoSe2 trion state conforms closely to the local CrBr3 magnetization, while the neutral exciton state remains insensitive to the ferromagnet. We attribute this to spin-dependent interlayer charge transfer occurring on timescales between the exciton and trion radiative lifetimes. Going further, we uncover by both the magneto-optical Kerr effect and photoluminescence a domain-like spatial topography of contrasting valley polarization, which we infer to be labyrinthine or otherwise highly intricate, with features smaller than 400 nm corresponding to our optical resolution. Our findings offer a unique insight into the interplay between short-lived valley excitons and spin-dependent interlayer tunneling, while also highlighting MoSe2 as a promising candidate to optically interface with exotic spin textures in van der Waals structures.

Many-body perturbation theory calculations using the yambo code.

yambo is an open source project aimed at studying excited state properties of condensed matter systems from first principles using many-body methods. As input, yambo requires ground state electronic structure data as computed by density functional theory codes such as Quantum ESPRESSO and Abinit. yambo's capabilities include the calculation of linear response quantities (both independent-particle and including electron-hole interactions), quasi-particle corrections based on the GW formalism, optical absorption, and other spectroscopic quantities. Here we describe recent developments ranging from the inclusion of important but oft-neglected physical effects such as electron-phonon interactions to the implementation of a real-time propagation scheme for simulating linear and non-linear optical properties. Improvements to numerical algorithms and the user interface are outlined. Particular emphasis is given to the new and efficient parallel structure that makes it possible to exploit modern high performance computing architectures. Finally, we demonstrate the possibility to automate workflows by interfacing with the yambopy and AiiDA software tools.

Fermi energy dependence of the optical emission in core/shell InAs nanowire homostructures.

InAs nanowires grown by vapor-liquid-solid (VLS) method are investigated by photoluminescence. We observe that the Fermi energy of all samples is reduced by ∼20 meV when the size of the Au nanoparticle used for catalysis is increased from 5 to 20 nm. Additional capping with a thin InP shell enhances the optical emission and does not affect the Fermi energy. The unexpected behavior of the Fermi energy is attributed to the differences in the residual donor (likely carbon) incorporation in the axial (low) and lateral (high incorporation) growth in the VLS and vapor-solid (VS) methods, respectively. The different impurity incorporation rate in these two regions leads to a core/shell InAs homostructure. In this case, the minority carriers (holes) diffuse to the core due to the built-in electric field created by the radial impurity distribution. As a result, the optical emission is dominated by the core region rather than by the more heavily doped InAs shell. Thus, the photoluminescence spectra and the Fermi energy become sensitive to the core diameter. These results are corroborated by a theoretical model using a self-consistent method to calculate the radial carrier distribution and Fermi energy for distinct diameters of Au nanoparticles.

Anisotropic optical response of GaN and AlN nanowires.

We present a theoretical study of the electronic structure and optical properties of free-standing GaN and AlN nanowires. We have implemented the empirical tight-binding method, with an orbital basis sp(3), that includes the spin-orbit interaction. The passivation of the dangling bonds at the free surfaces is also studied, together with the effects on the electronic structure of the nanowire. For both GaN and AlN nanowires, we have found a remarkable anisotropy of the optical absorption when the light-polarization changes, showing in the case of GaN a dependence on the nanowire size.

[Lipoma of the stomach. Presentation of a case and a review of cases reported in Spain]. / Lipoma gástrico. Presentación de un caso y revisión de la casuística en España.

Gastric lipoma is an infrequent benign submucosal tumor that is usually asymptomatic. In view of the few reports of this pathology in the Spanish and international bibliography, a new case that debuted as massive upper gastrointestinal hemorrhage is communicated. We reviewed the cases published in Spain to date, emphasizing the methodology of preoperative diagnosis, with special attention to the endoscopic signs characterizing gastric lipoma and computerized axial tomography, which is now viewed as the technique of choice. Therapeutic options are discussed.

[Lactic acidosis in recovered asphyctic newborn infants]. / Acidosis láctica en el recién nacido asfíctico recuperado.

Thirty newborn babies delivered by elective caesarean section were studied. They were randomly placed in two groups. The first group consisted of newborns who scored 3 or less on the Apgar scale at one minute and 8 or more after five minutes. The other group included newborns which scored 8 or higher at one minute and 9 at five minutes. Blood samples were obtained from the umbilical cord which allowed for the measuring of the infants' pH, serum gases and pyruvic lactic acid levels. An increased level lactate was found in asphyctic infants. Five cases presented lactic acidosis which continued to be persistent in four of them an hour after they were born. Although increased levels of lactate were found also in the control group, they never presented lactic acidosis. No correlation was found between the pH and lactate levels nor between lactate and bicarbonate. A clear correlation between lactic acidosis and fetal distress was documented. It was concluded that lactate quantification is a useful indicator of neonatal asphyxia. Lactic acidosis; Apgar scores; asphyxia.