Functional renormalization group study of parallel double quantum dots: Effects of asymmetric dot-lead couplings

We explore the effects of asymmetry of hopping parameters between double parallel quantum dots and the leads on the conductance and a possibility of local magnetic moment formation in this system using functional renormalization group approach with the counterterm. We demonstrate a possibility of a quantum phase transition to a local moment regime (so called singular Fermi liquid (SFL) state) for various types of hopping asymmetries and discuss respective gate voltage dependences of the conductance. It is shown, that depending on the type of the asymmetry, the system can demonstrate either a first order quantum phase transition to SFL state, accompanied by a discontinuous change of the conductance, similarly to the symmetric case, or the second order quantum phase transition, in which the conductance is continuous and exhibits Fano-type asymmetric resonance near the transition point. A semi-analytical explanation of these different types of conductance behavior is presented.Comment: 11 pages, 9 figure

Local magnetic moments and electronic transport in closed loop quantum dot systems: a case of quadruple quantum dot ring at and away from equilibrium

We apply the non-equilibrium functional renormalization group approach treating flow of the electronic self-energies, to describe local magnetic moments formation and electronic transport in a quadruple quantum dot (QQD) ring, coupled to leads, with moderate Coulomb interaction on the quantum dots. We find that at zero temperature depending on parameters of the QQD system the regimes with zero, one, or two almost local magnetic moments in the ring can be realized, and the results of the considered approach in equilibrium agree qualitatively with those of more sophisticated fRG approach treating also flow of the vertices. It is shown that the almost formed local magnetic moments, which exist in the equilibrium, remain stable in a wide range of bias voltages near equilibrium. The destruction of the local magnetic moments with increasing bias voltage is realized in one or two stages, depending on the parameters of the system; for two-stage process the intermediate phase possesses fractional magnetic moment. We present zero-temperature results for current-voltage dependences and differential conductances of the system, which exhibit sharp features at the transition points between different magnetic states. The occurrence of interaction induced negative differential conductance phenomenon is demonstrated and discussed. For one local moment in the ring and finite hopping between the opposite quantum dots, connected to the leads, we find suppression of the conductance for one of the spin projections in infinitesimally small magnetic field, which occurs due to destructive interference of different electron propagation paths and can be used in spintronic devices.Comment: 19 pages, 19 figure

Transition absorption as a mechanism of surface photoelectron emission from metals

Transition absorption of electromagnetic field energy by an electron passing through a boundary between two media with different dielectric permittivities is considered both classically and quantum mechanically. It is shown that transition absorption can make a substantial contribution to the process of electron photoemission from metals due to the surface photoelectric effect.Comment: 4 pages, 3 figure

Oscillator laser model

A laser model is formulated in terms of quantum harmonic oscillators. Emitters in the low lasing states are usual harmonic oscillators, and emitters in the upper states are inverted harmonic oscillators. Diffusion coefficients, consistent with the model and necessary for solving quantum nonlinear laser equations analytically, are found. Photon number fluctuations of the lasing mode and fluctuations of the population of the lasing states are calculated. Collective Rabi splitting peaks are predicted in the intensity fluctuation spectra of the superradiant lasers. Population fluctuation mechanisms in superradiant lasers and lasers without superradiance are discussed and compared with each other.Comment: Preprint: 18 pages, 6 figures, 1 tabl

Digital Marketing in the Development of Pharmaceutical Companies: The Current Aspects and Perspectives

The article studies the modern aspects and prospects of using Digital marketing in the development of pharmaceutical companies. Digital marketing in the pharmaceutical industry has been found to help reach an expanded global customer base, providing multiple opportunities to enhance the promotion and sustainability of a pharmaceutical company. It was found that the practical tools of digital marketing are e-mail, electronic data detailing, augmented and virtual reality, the use of which reduces the costs of pharmaceutical companies. It was determined that due to modern conditions, pharmaceutical companies intensively use social network platforms for the promotion and branding of medicinal products. It was determined that such Digital marketing tactics as content marketing, search engine optimization, e-mail marketing, social media marketing, etc., are considered effective tools for the promotion of medicinal products. Digital marketing has been found to generate valuable information that has a significant impact on the pharmaceutical sector, so pharmaceutical companies build consumer satisfaction through phone applications and online networks, allowing the pharmaceutical company to increase sales and profits. It has been found that pharmaceutical companies are increasingly using social media as target customers increase public awareness of their drugs and services and seek more effective opportunities to engage with target audiences. It has been found that for pharmaceutical companies, the e-commerce platform is the foundation of their digital presence, and improving the customer-centric infrastructure with well-integrated systems will help ensure proper customer interaction. It has been determined that the benefits of social media and online marketing are particularly important for pharmaceutical companies, as they are crucial to ensure more effective digital marketing. It was established that following the results of January-June 2022, the pharmaceutical companies "Farmak", "Darnytsia" and "Acino" took the leading positions in terms of sales of medicinal products

Quantum fluctuations in the small Fabry-Perot interferometer

We consider the small, of the size of the order of the wavelength, interferometer with the main mode excited by a quantum field from a nano-LED or a laser. The input field is detuned from the interferometer mode with, on average, a few photons. We find the field and the photon number fluctuation spectra inside and outside the interferometer and identify the contributions of quantum and classical noise in the spectra. Structures of spectra are different for the field, the photon number fluctuations inside the interferometer; for the transmitted, and the reflected fields. We note asymmetries in spectra. Differences in the spectra are related to the colored (white) quantum noise inside (outside) the interferometer. We calculate the second-order time correlation functions; they oscillate and be negative under certain conditions. Results help the study, design, manufacture, and use small elements of quantum optical integrated circuits, such as delay lines and optical transistors.Comment: 16 pages, 9 figure