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Abstract We theoretically investigate the electron and hole states in a semiconductor quantum dot-quantum ring coupled structure, inspired by the recent experimental report by Elborg and collaborators (2017). The finite element method constitutes the numerical technique used to solve the three-dimensional effective mass equation within the parabolic band approximation, including the effects of externally applied electric and magnetic fields. Initially, the features of conduction electron states in the proposed system appear discussed in detail, under different geometrical configurations and values of the intensity of the aforementioned electromagnetic probes. In the second part, the properties of an electron-hole pair confined within the very kind of structure reported in the reference above are investigated via a model that tries to reproduce as close as possible the developed profile. In accordance, we report on the energies of confined electron and hole, affected by the influence of an external electric field, revealing the possibility of field-induced separate spatial localization, which may result in an indirect exciton configuration. In relation with this fact, we present a preliminary analysis of such phenomenon via the calculation of the Coulomb integral.

We study the linear, third-order nonlinear, and total absorption coefficients (OACs) caused by intra- and inter-band transitions in monolayer MoSe2 in the presence of a magnetic field by using the compact density matrix approach. The results show that the OACs display the blue-shift behaviour with an increase in the magnetic field. The Zeeman fields do not affect the peak positions but reduce peak intensities slightly. Besides, the strong spin-orbit coupling in monolayer MoSe2 causes the peaks to differ significantly due to spin-up and spin-down. The OACs due to intra-band transition display only one peak in the THz range, while the inter-band spectra show a series of peaks in the near-infrared optical range, making monolayer MoSe2 a promising candidate for novel optoelectronic applications.

In this work, we theoretically investigate electronic properties of GaSeMoS2 and GaSMoSe2 heterojunctions using density functional theory based on first-principles calculations. The results show that both GaSeMoS2 and GaSMoSe2 heterojunctions are characterized by the weak vdW interactions with a corresponding interlayer distance of 3.45 Å and 3.54 Å, and the binding energy of −0.16 eV per GaSeGaS cell. Furthermore, one can observe that both the GaSeMoS2, and GaSMoSe2 heterojunctions are found to be indirect band gap semiconductors with a corresponding band gap of 1.91 eV and 1.23 eV, respectively. We also find that the band gaps of these semiconductors belong to type II band alignment. A type–II band alignment in both GaSeMoS2 and GaSMoSe2 heterojunctions open their potential applications as novel materials such as in designing and fabricating new generation of photovoltaic and optoelectronic devices.

The empirical results of this study reveal the following interesting characteristics of the Romanian banking sector over the December 1993 through August 2017 period. First, the spread between the lending-Central Bank’s discount rates was stable and adjusted to its long-run threshold asymmetrically. Second, lending institutions respond faster to contractionary than expansionary countercyclical monetary policy actions. This empirical finding suggests that Romanian commercial banks exhibit predatory rate setting behavior, which is consistent with those of their counterparts in advanced and emerging economies. Third, lending institutions respond to countercyclical monetary policy and the Romanian Central Bank authority effectively utilizes monetary policy to manage the economy as evidenced by the short-run dynamic and long-run Granger-causality from the discount rate to the banks’ lending rate. With respect to the time lags of the Romanian monetary policy found within the banking sector, the empirical results suggest that it takes almost two years for the lending rate to adjust to a monetary policy action completely.

We study the magneto-optical properties of Dirac semimetal (DSM) slabs with particular emphasis on Cd 3 As 2 through electron–photon–phonon interactions, focusing on the magneto-optical absorption coefficient (MOAC) and full-width at half maximum (FWHM). Studying the Landau level (LL) energy of DSMs in the (x y) plane and the z -direction revealed a unique deviation from the square root dependence on the magnetic field, distinguishing DSMs from other semiconductors. At high magnetic fields, the electron–hole symmetry in the LL spectrum is broken, indicating a topological phase in DSMs. For undoped DSMs, MOAC is driven by interband transitions, with peaks from one-photon absorption being smaller and positioned to the left of two-photon ones. Increasing the magnetic field increases peak values. FWHM for one- and two-photon processes increases with the magnetic field and follows a T dependence on temperature. In doped DSMs, both intraband and interband transitions occur, with new interband peaks emerging at higher temperatures near the Fermi energy. Increased electron density shifts the peak position slightly toward higher energy. Peaks from optical phonon emission are consistently higher and located to the right of those from optical phonon absorption, indicating a stronger emission process. The FWHM data allow for the estimation of electron mobilities, and using a reasonable broadening parameter, our predicted mobility values agree with experimental results. [ABSTRACT FROM AUTHOR]

The absolute photoabsorption cross sections of norbornadiene (NBD) and quadricyclane (QC), two isomers with chemical formula C7H8 that are attracting much interest for solar energy storage applications, have been measured from threshold up to 10.8 eV using the Fourier transform spectrometer at the SOLEIL synchrotron radiation facility. The absorption spectrum of NBD exhibits some sharp structure associated with transitions into Rydberg states, superimposed on several broad bands attributable to valence excitations. Sharp structure, although less pronounced, also appears in the absorption spectrum of QC. Assignments have been proposed for some of the absorption bands using calculated vertical transition energies and oscillator strengths for the electronically excited states of NBD and QC. Natural transition orbitals indicate that some of the electronically excited states in NBD have a mixed Rydberg/valence character, whereas the first ten excited singlet states in QC are all predominantly Rydberg in the vertical region. In NBD, a comparison between the vibrational structure observed in the experimental 11B1–11A1 (3sa1 ← 5b1) band and that predicted by Franck–Condon and Herzberg–Teller modeling has necessitated a revision of the band origin and of the vibrational assignments proposed previously. Similar comparisons have encouraged a revision of the adiabatic first ionization energy of NBD. Simulations of the vibrational structure due to excitation from the 5b2 orbital in QC into 3p and 3d Rydberg states have allowed tentative assignments to be proposed for the complex structure observed in the absorption bands between ∼5.4 and 7.0 eV. [ABSTRACT FROM AUTHOR]

This study addresses the effect of electron–phonon coupling (EPC) on the electro-optical properties of gated β12-borophene. The focus is on how EPC influences the orbital hybridization of boron atoms, particularly within the Bariśic–Labbe–Friedel–Su–Schrieffer–Heeger framework, and considers the role of gate electrodes in this process. The results reveal a redshift in the optical spectrum only when there is positive feedback from one electrode on EPC. In other configurations, except for the y-direction, a blueshift spectrum is observed. The study emphasizes the importance of tuning these spectral shifts for maximizing the performance of solar cells in converting sunlight into usable energy. [ABSTRACT FROM AUTHOR]

In this study, using the tight-binding model and Green's function technique, we investigate potential electronic phase transitions in bilayer P6mmm borophene under the influence of external stimuli, including a perpendicular electric field, electron–hole coupling between sublayers (excitonic effects), and dopants. Our focus is on key electronic properties such as the band structure and density of states. Our findings reveal that the pristine lattice is metal with Dirac cones around the Fermi level, where their intersection forms a nodal line. The system undergoes transitions to a semiconducting state – elimination of nodal line – with a perpendicular electric field and a semimetallic state – transition from two Dirac cones to a single Dirac cone – with combined electric field and excitonic effects. Notably, with these, the system retains its massless Dirac-like bands characteristic at finite energy. However, introducing a dopant still leads to a metallic phase, but the Dirac-like bands become massive. Considering all these effects, the system ultimately reaches a semiconducting phase with massive Dirac-like bands. These results hold significance for optoelectronic applications. [ABSTRACT FROM AUTHOR]