Kondo and Dicke effect in quantum-dots side coupled to a quantum wire

Electron tunneling through quantum-dots side coupled to a quantum wire, in equilibrium and nonequilibrium Kondo regime, is studied. The mean-field finite-$U$ slave-boson formalism is used to obtain the solution of the problem. We have found that the transmission spectrum shows a structure with two anti-resonances localized at the renormalized energies of the quantum dots. The DOS of the system shows that when the Kondo correlations are dominant there are two Kondo regimes with its own Kondo temperature. The above behavior of the DOS can be explained by quantum interference in the transmission through the two different resonance states of the quantum dots coupled to common leads. This result is analogous to the Dicke effect in optics. We investigate the many body Kondo states as a function of the parameters of the system.Comment: 5 figures. To appear in Phys. Rev.

Beyond symmetry-protected BICs: transmission through asymmetric crossbar junctions in one-dimensional waveguides

Over the last few decades, the study of Bound States in the Continuum, their formation, and properties has attracted lots of attention, especially in optics and photonics. It is particularly noticeable that most of these investigations base their studies on symmetric systems. In this article, we study the formation of bound states in the continuum in electronic and photonic transport systems consisting of crossbar junctions formed by one-dimensional waveguides, considering asymmetric junctions with commensurable lengths for the upper and lower arms. We also study how BICs form in linear junction arrays as a function of the distance between consecutive junctions and their commensurability with the upper and lower arms. We solve the Helmholtz equation for the crossbar junctions and calculate the transmission probability, probability density in the intersections, and quality factor. The presence of quasi-BICs is reflected in the transmission probability as a sharp resonance in the middle of a symmetric Fano resonance along with Dirac's delta functions in the probability density and divergence in the quality factors.Comment: 12 pages, 12 figure

Kondo effect in a double quantum-dot molecule under the effect of an electric and magnetic field

Electron tunneling through a double quantum dot molecule, in the Kondo regime, under the effect of a magnetic field and an applied voltage, is studied. This system possesses a complex response to the applied fields characterized by a tristable solution for the conductance. The different nature of the solutions are studied in and out thermodynamical equilibrium. It is shown that the interdot coupling and the fields can be used to control the region of multistability. The mean-field slave-boson formalism is used to obtain the solution of the problem.Comment: 5 pages, 4 figures. To appear in Sol. State Com

Anomalous spin textures in a 2D topological superconductor induced by point impurities

Topological superconductors are foreseen as good candidates for the search of Majorana zero modes, where they appear as edge states and can be used for quantum computation. In this context, it becomes necessary to study the robustness and behavior of electron states in topological superconductors when a magnetic or non-magnetic impurity is present. We focus on scattering resonances in the bands and on spin texture to know what the spin behavior of the electrons in the system will be. We find that the scattering resonances appear outside the superconducting gap, thus providing evidence of topological robustness. We also find non-trivial and anisotropic spin textures related to the Dzyaloshinskii-Moriya interaction. The spin textures show a Ruderman-Kittel-Kasuya-Yosida interaction governed by Friedel oscillations. We believe that our results are useful for further studies which consider many-point-impurity scattering or a more structured impurity potential with a finite range

Fano-Andreev effect in a T-shaped Double Quantum Dot in the Coulomb blockade regime

We studied the effects of superconducting quantum correlations in a system consisting of two quantum dots, two normal leads, and a superconductor. Using the non-equilibrium Green's functions method, we analyzed the transmission, density of states, and differential conductance of electrons between the normal leads. We found that the superconducting correlations resulted in Fano-Andreev interference, which is characterized by two anti-resonance line shapes in all of these quantities. This behavior was observed in both equilibrium and non-equilibrium regimes and persisted even when Coulomb correlations were taken into account using the Hubbard-I approximation. It is worth noting that the robustness of this behavior against these conditions has not been studied previously in the literature.Comment: 14 pages, 12 figure