We studied the performance of classical and quantum magnetic Otto cycle with a working substance composed of a single quantum dot using the Fock–Darwin model with the inclusion of the Zeeman interaction. Modulating an external/perpendicular magnetic field, in the classical approach, we found an oscillating behavior in the total work extracted that was not present in the quantum formulation.We found that, in the classical approach, the engine yielded a greater performance in terms of total work extracted and efficiency than when compared with the quantum approach. This is because, in the classical case, the working substance can be in thermal equilibrium at each point of the cycle, which maximizes the energy extracted in the adiabatic strokes.

In this work, we investigate the spin and valley transport properties of a $\mathrm{W}{\mathrm{Se}}_2$ monolayer placed on top of a ferromagnetic insulator. We are interested in controlling the transport properties by applying external potentials to the system. To obtain spin and valley polarizations, we consider a single- and a double-barrier structure with gate potentials. We analyze how the efficiency of these polarized transport properties depends on the gate-potential intensities and geometrical configurations. Additionally, we investigate how the spin and valley transport properties are modified when an ac potential is applied to the system. We obtain a controllable modulation of the spin and valley polarizations as a function of the intensity and frequency of the ac potential, mainly in the terahertz range. These results validate the proposal of double quantum well structures of $\mathrm{W}{\mathrm{Se}}_2$ as candidates to provide spin- and valley-dependent transport within an optimal geometrical parameter regime.

In this work, we study the bound states in the continuum (BICs) in a system formed by a triple quantum dot array embedded between two one-dimensional topological superconductors (TSCs), both hosting Majorana bound states (MBSs) at their ends. The results show the formation of BICs with topological characteristics due to the presence of MBSs. This is a consequence of the interplay between the BIC arising from quantum dots states by means of energy level symmetry breaking through gate voltages, and MBSs leaked into the quantum dots. The BIC is not observed when both TSCs are in long wire limit, i.e. for vanishing inter MBSs coupling, while it projects into the electronic transmission whenever the inter MBSs couplings are away from zero, regardless if they have different strength and/or the phase difference between both TSCs. We study the behavior of BICs poisoned by MBSs as a function of the parameters that are controlling the system. We believe our findings could be useful to implement a protection tool for BICs using MBSs based on tunable gate voltages.

We study the performance of a classical and quantum magnetic Otto cycle with a quantum dot as a working substance using the Fock-Darwin model with the inclusion of the Zeeman interaction. Modulating an external/perpendicular magnetic field, we found in the classical approach an oscillating behavior in the total work that is not perceptible under the quantum formulation. Also, we compare the work and efficiency of this system for different regions of the Entropy, $S(T,B)$, diagram where we found that the quantum version of this engine always shows a reduced performance in comparison to his classical counterpart.

With an appropriate mixture of cyclometalating and ancillary ligands, based on simple structures (commercial or easily synthesized), it has been possible to design a family of eight new Ir(III) complexes (1A, 1B, 2B, 2C, 3B, 3C, 3D and 3E) useful as luminescent materials in LEC devices. These complexes involved the use of phenylpyridines or fluorophenylpyridines as cyclometalating ligands and bipyridine or phenanthroline-type structures as ancillary ligands. The emitting properties have been evaluated from a theoretical approach through Density Functional Theory and Time-Dependent Density Functional Theory calculations, determining geometric parameters, frontier orbital energies, absorption and emission energies, injection and transport parameters of holes and electrons, and parameters associated with the radiative and non-radiative decays. With these complexes it was possible to obtain a wide range of emission colours, from deep red to blue (701–440 nm). Considering all the calculated parameters between all the complexes, it was identified that 1B was the best red, 2B was the best green, and 3D was the best blue emitter. Thus, with the mixture of these complexes, a dual host–guest system with 3D-1B and an RGB (red–green–blue) system with 3D-2B-1B are proposed, to produce white LECs.