Karol I. Wysokinski

Electron transport through a strongly interacting quantum dot coupled to a normal metal and BCS superconductor

We study electron transport through a quantum dot coupled to a normal metal and BCS-like superconductor (N–QD–S) in the presence of the Kondo effect and Andreev scattering. The system is described by the single impurity Anderson model in the limit of strong on-dot interaction. To study electron transport, we use the recently proposed equation of motion technique for the Keldysh non-equilibrium Greens function together with the modified slave boson approach. We derive the formula for the current which contains various tunnelling processes and we apply it to a study of the transport through the system. We find that the Andreev conductance is strongly suppressed and there is no zero-bias (Kondo) anomaly in the differential conductance. We discuss the effects of the particle–hole asymmetry in the electrodes as well as the asymmetry in the couplings.

Analytic investigation of holographic phase transitions influenced by dark matter sector

We analytically study the phase transitions between s-wave holographic insulator/superconductor and metal/superconductor. The problem is solved by the variational method for the Sturm-Liouville eigenvalue problem in the theory with dark matter sector of U(1)-gauge field coupled to the Maxwell field. Additionally in the probe limit we investigate the marginally stable modes of scalar perturbations in the AdS solitonic background, connected with magnetic field in the dark matter sector. We have found that even with dark matter sector the superconducting transition temperature

Magnetic field in holographic superconductor with dark matter sector

T_c

P-wave holographic superconductor/insulator phase transitions affected by dark matter sector

is proportional to charge density

Holographic vortices in the presence of dark matter sector

\rho

Thermoelectric effects in strongly interacting quantum dot coupled to ferromagnetic leads

in power 1/3. This value seem to be strong coupling modification of the exponent 2/3 known from the Bose - Einstein condensation of charged local pair bosons in narrow band superconductors. The holographic droplet solution is affected by the coupling to the dark matter. Interestingly in the probe limit the critical chemical potential increases with the decreasing coupling to dark matter making the condensation transition harder to appear.

Interplay between direct and crossed Andreev reflections in hybrid nanostructures

Based on the analytical technique the effect of the static magnetic field on the s-wave holographic superconductor with dark matter sector of U(1)-gauge field type coupled to the Maxwell field has been examined. In the probe limit, we obtained the mean value of the condensation operator. The nature of the condensate in an external magnetic field as well as the behavior of the critical field close to the transition temperature has been revealed. The obtained upturn of the critical field curves as a function of temperature, both in four and five spacetime dimensions, is a fingerprint of the strong coupling approach.

Condensate flow in holographic models in the presence of dark matter

A bstractThe holographic approach to building the p-wave superconductors results in three different models: the Maxwell-vector, the SU(2) Yang-Mills and the helical. In the probe limit approximation, we analytically examine the properties of the first two models in the theory with dark matter sector. It turns out that the effect of dark matter on the Maxwell-vector p-wave model is the same as on the s-wave superconductor studied earlier. For the non-Abelian model we study the phase transitions between p-wave holographic insulator/superconductor and metal/superconductor. Studies of marginally stable modes in the theory under consideration allow us to determine features of p-wave holographic droplet in a constant magnetic field. The dependence of the superconducting transition temperature on the coupling constant α to the dark matter sector is affected by the dark matter density ρD . For ρD> ρ the transition temperature is a decreasing function of α. The critical chemical potential μc for the quantum phase transition between insulator and metal depends on the chemical potential of dark matter μD and for μD = 0 is a decreasing function of α.

Interorbital pair scattering in two-band superconductors

A bstractThe dark matter seem to be an inevitable ingredient of the total matter configuration in the Universe and the knowledge how the dark matter affects the properties of superconductors is of vital importance for the experiments aimed at its direct detection. The homogeneous magnetic field acting perpendicularly to the surface of (2+1) dimensional s-wave holographic superconductor in the theory with dark matter sector has been modeled by the additional U(1)-gauge field representing dark matter and coupled to the Maxwell one. As expected the free energy for the vortex configuration turns out to be negative. Importantly its value is lower in the presence of dark matter sector. This feature can explain why in the Early Universe first the web of dark matter appeared and next on these gratings the ordinary matter forming cluster of galaxies has formed.

Optimisation of a three-terminal nonlinear heat nano-engine

We study thermoelectric effects in Kondo correlated quantum dot coupled to ferromagnetic electrodes by calculating thermopower S in the Kondo regime as function of on-dot energy level and temperature. The system is represented by the Anderson model and the results agree well with those recently measured for a quantum dot coupled to nonmagnetic leads. For magnetic electrodes, one observes marked dependence of S on the degree of their polarisation.