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1
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Pseudogap and Other Precursor Signatures in the Systems with Local Fermion Pairs

100%
Domański T.
Acta Physica Polonica A
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2004
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vol. 106
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issue 5
553-560
EN
We consider precursor effects of the superconducting order which possibly show up in the normal state of high temperature superconducting materials. The local pairs of electrons or holes are formed there well above the transition temperature T_c. Due to strong quantum fluctuations the single particle density of states can be partly depleted near the Fermi energy leading to the pseudogap. We claim that this feature should go hand in hand with emergence of the Bogoliubov-type quasiparticles. In the normal state they are expected to be damped and acquire the long lifetime upon passing T_c. These Bogoliubov-type quasiparticles may nevertheless become correlated on a finite spatial and temporal scale. We discuss how such short-range pair correlations can be detected experimentally.
2
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On Realization of the Bose-Einstein Condensates and Quantum Superfluids

100%
Domański T.
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issue 2
204-211
EN
The purpose of this work is twofold. In the first part we describe superfluidity/superconductivity as an emergent phenomenon resulting from two-body correlations in presence of the Bose-Einstein condensation of particles. We briefly discuss the underlying mechanism for bosons as well as fermion pairs and illustrate various realizations of superfluidity emphasizing the recent examples. In the second part we study the glassy liquid of incoherent pairs which might exist above the transition temperature T_{c} in the underdoped regime of cuprate superconductors. In particular, we explore the angular variation of pseudogap within two-dimensional version of the boson-fermion model using for a quantitative analysis the projective method. We find that above T_{c} the pseudogap closes first near the nodal areas restoring there pieces (arcs) of the Fermi surface whereas remaining parts of the large Fermi surface around the antinodal points are still absent due to incoherent pairs. Upon increasing temperature the length of the Fermi arcs enlarges because the superconducting correlations are gradually suppressed. An intriguing death of Fermi surface can thus be closely related to the Bogoliubov quasiparticles whose existence in the pseudogap state has been predicted by us and confirmed recently by the angle resolved photoemission spectroscopy measurements on Bi_2Sr_2CaCu_2O_8 and La_{1.895}Sr_{0.105}CuO_4 compounds.
3
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Numerical analysis of thermo-mechanical phenomena of the progressive hardening elements madeof tool steel for cold work

100%
Domański T.
Archives of Metallurgy and Materials
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2019
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vol. 64
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issue 1
4
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Probability calibration of load duration modificationfactor for timber roofs in the polish mountain zones

100%
Domański T.
Archives of Civil Engineering
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2014
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issue 2
5
Content available remote

The In-Gap Charge Current through the Correlated Quantum Dot Hybridized with Superconductor

64%
Donabidowicz A., Domański T.
Acta Physica Polonica A
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2008
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vol. 114
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issue 1
75-82
EN
We explore the Andreev tunnelling through the strongly correlated quantum dot embedded between the normal and superconducting electrodes. For a small external voltage |eV| <∆_s the electron arriving from the normal lead can be converted into a pair on the quantum dot and further propagates in the superconducting lead while simultaneously the hole is reflected back to the normal electrode. Conductance of such anomalous current is very sensitive to the particle-hole mixing of the quantum dot spectrum. We analyze the influence of the proximity effect and the Coulomb interactions on the differential Andreev conductance focusing on the extreme limit ∆_s → ∞.
6
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Single Particle Excitation Spectrum of a Proximized Quantum Dot: The Flow Equation Study

64%
Zapalska M., Domański T.
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vol. 126
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issue 4a
A-137-A-140
EN
We study the in-gap states of a quantum dot hybridized with the metallic and superconducting reservoirs applying the continuous unitary transformation to the Anderson-type Hamiltonian. We derive the set of flow equations and analyse the effective single particle excitation spectrum of the correlated quantum dot in presence of the induced electron pairing.
7
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Fluctuations between the BCS and BEC Limits in the System of Ultracold Alkali Atoms

64%
Domański T., Donabidowicz A.
Acta Physica Polonica A
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2006
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vol. 109
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issue 4-5
471-476
EN
We investigate the fluctuations induced by time-dependent interchange between the Bardeen-Cooper-Schrieffer and Bose-Einstein condensation regimes in the ultracold gas of fermion atoms. Such crossover can be triggered by varying the external magnetic field across the Feshbach resonance. Experimental realization is usually done via very fast switching which leads to the nonequilibrium effects. In this paper we focus on the ground state properties. In particular, we analyze time dependence of the wave function and consider fluctuations of the order parameters.
8
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Numerical Models of Hardening Phenomena of Tools Steel Base on the TTT and CCT Diagrams Modele numeryczne zjawisk hartowania stali narzędziowej oparte na wykresach CTPi oraz CTPc

64%
Domański T., Bokota A.
Archives of Metallurgy and Materials
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2011
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issue 2
9
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Interplay between the Correlations and Superconductivity in Electron Transport through the Double Quantum Dots

64%
Barański J., Domański T.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1213-1215
EN
We study the influence of electron correlations on nonequilibrium transport through the quantum dots coupled between one metallic and one superconducting electrode. Such type of nanodevices are characterized by the induced on-dot pairing spread from the superconducting lead (proximity effect) and effectively responsible for mixing the particle with hole excitations. On the other hand, strong Coulomb repulsion between the opposite spin electrons tends to suppress a double occupancy of the quantum dots competing with the on-dot superconducting order. The Coulomb interactions can also cause a screening of the quantum dot spin by itinerant electrons of the metallic lead giving rise to formation of the Kondo resonance. We analyze interplay of such phenomena for the setup of double quantum dots where the quantum interference (such as Fano) effects influence the subgap electron transport through the Andreev scattering.
10
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Interference Effects on Double Quantum Dots Coupled Between Metallic and Superconducting Leads

64%
Barański J., Domański T.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
812-815
EN
We describe the quantum interference effects in the nanodevice consisting of the double quantum dot coupled to the metallic and superconducting electrodes. In such heterostructures the superconducting properties are spread to the quantum dot due to the proximity effect. We investigate the density of states and anomalous Andreev conductance of the interfacial quantum dot exploring the conditions necessary for appearance of the Fano-type lineshapes. We also consider the electron correlations and discuss an interplay between the Coulomb blockade and the Fano-type interference.
11
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Tunneling through the Quantum Dot Coupled to Incoherent Superconductor

64%
Donabidowicz A., Domański T.
Acta Physica Polonica A
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2007
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vol. 111
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issue 5
671-682
EN
We study the equilibrium and non-equilibrium properties of the strongly correlated quantum dot coupled between normal and superconducting leads. The effect of electron pair coherence, Coulomb interactions, and d-wave anisotropy of the order parameter are discussed with a particular account of their influence on a charge tunneling through the quantum dot.
12
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Renormalization Group Approach for the Double Exchange Ferromagnets

64%
Zapalska M., Domański T.
Acta Physica Polonica A
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2012
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vol. 122
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issue 6
1099-1101
EN
The discovery of the colossal magnetoresistance (CMR) in the manganese oxides with perovskite structures T_1 - x DMnO_3 (T = La, Pr, Nd; D=Sr, Ca, Ba, Pb) and its potential technological application motivated theoretical and experimental researchers to study the itinerant ferromagnetism. A first theoretical description of this phenomenon in terms of the double-exchange mechanism was given a long time ago by Zener. In this model, the spin orientation of adjacent Mn-moments is associated with kinetic exchange of conduction e_g electrons. Consequently, alignment of the core Mn-spins by an external magnetic field causes higher conductivity. The Mn ions are considered as localized forming a spin of S = 3/2 and they are coupled to the itinerant electrons by a strong ferromagnetic Hund coupling, J_H > 0. We apply the flow equation technique (nonperturbative method, based on continuous canonical transformation) to the double-exchange model for ferromagnetism described by the Kondo type Hamiltonian. We want to eliminate the interaction term responsible for non-conservation of magnon number and to take into account fermion and magnon degrees of freedom. We express the spin operators of Mn ions via the magnon operators (the Holstein-Primakoff transformation) and investigate the magnon excitation spectrum determined by Green's function.
13
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Subgap Current through the Strongly Correlated Quantum Dot Hybridized with the Normal and Superconducting Leads

64%
Domański T., Donabidowicz A.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
86-88
EN
We investigate charge tunneling through the strongly correlated quantum dot placed between the metallic and superconducting leads. For small voltages |V| ≤ Δ/e applied across the junction the current is transmitted by the anomalous mechanism of the Andreev reflections. Such transport is sensitive to the strong Coulomb interactions which can be responsible for the charging effect and, at low temperatures, for appearance of the Kondo resonance. We analyze their signatures in the differential Andreev conductance.
14
Publication available in full text mode
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Numerical Models of Hardening Phenomena of Tools Steel Base on the TTT and CCT Diagrams

64%
Domański T., Bokota A.
Archives of Metallurgy and Materials
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2011
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issue 2
15
Content available remote

Electromagnetic Response of the BCS Superconductor: Flow Equation Approach

64%
Zapalska M., Domański T.
Acta Physica Polonica A
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2012
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vol. 121
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issue 4
854-857
EN
We address the linear response for superconductors using the non-perturbative technique based on the continuous unitary transformation. We discuss how this method rigorously reproduces the standard BCS solution and point out how such result can be generalized to the case of electron systems with strong pairing fluctuations and in presence of the nonequilibrium phenomena.
16
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Phonon Signatures of a Quantum Impurity with Induced Electron Pairing

64%
Barański J., Domański T.
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vol. 126
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issue 4a
A-73-A-76
EN
We analyze the effective spectrum of a vibrating molecule coupled between one conducting and another superconducting electrode. The proximity effect induces electron pairing which is manifested by the subgap quasiparticle peaks (the Andreev states) whose broadening depends on a hybridization with the conducting electrode. On the other hand, the electron-phonon interaction leads to a multilevel structure with the polaronic states separated by the phonon energy. We inspect a combined effect of both these (polaronic and induced pairing) phenomena.
17
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Statistics of Tunneling Events in Three-Terminal Hybrid Devices with Quantum Dot

52%
Michałek G., Bułka B., Domański T., Wysokiński K.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
391-393
EN
We investigate statistics of the tunneling events in the short time limit in terms of the waiting time distribution (WTD), defined as the probability for a delay time between two subsequent transitions of particles, and consider it for a quantum dot (QD) strongly coupled to a superconducting and weakly coupled to two normal electrodes. Our study focuses on the WTD in the subgap transport, when coherent exchange of the Cooper pairs occurs between the QD and the superconductor. The dynamics can be described in terms of a Markovian generalized master equation for the reduced density matrix. We observe coherent oscillations between the Andreev bound states in the correlated jumps, both for the local and non-local WTDs. In addition the analysis of the transient currents give us some insight into dominant relaxation processes in short time scales.
18
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Tunneling through the Quantum Dot Coupled between Normal and Superconducting Leads

52%
Donabidowicz A., Domański T., Wysokiński K.
Acta Physica Polonica A
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2007
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vol. 112
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issue 2
157-160
EN
We study the charge tunneling via the quantum dot coupled to normal and superconducting leads, where the superconducting electrode has either an isotropic or anisotropic (of d-wave symmetry) energy gap. We use the single impurity Anderson model and apply the nonequilibrium Green function formalism to determine the differential tunneling conductance. The influence of the proximity effect between the quantum dot and superconductor on the transport properties of the system manifests itself in the Andreev conductance.
19
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Do Van Hove Singularities in Leads Influence Tunneling Current through Quantum Dot?

52%
Krawiec M., Domański T., Wysokiński K.
Acta Physica Polonica A
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1998
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vol. 94
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issue 3
411-414
EN
Using the Landauer type formula for the current through quantum dot we have studied the influence of the singularities in the density of states in leads on the differential conductance of the system and answered affirmatively the above question. The presence of Van Hove singularities in the leads may induce an additional structure on the conductance vs. voltage curve. The dot itself has been described by the single impurity Anderson model with a very strong "on-dot" Coulomb repulsion. We also simulate the effect of electron-phonon interaction in the dot by allowing for the fluctuations of the "impurity" energy level.
20
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Inhomogeneities in Superconductors Described by the Two-Component Model

52%
Krzyszczak J., Domański T., Wysokiński K.
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issue 2
360-363
EN
We study fluctuations of the superconducting order parameter of s-wave symmetry caused by nonmagnetic disorder present both in the boson and fermion subsystems using the Bogoliubov-de Gennes equations. In particular, we are interested if some features of the d-wave model persist for s-wave symmetry as well. These are: positive correlations between positions of impurities and the magnitude of energy gap, the homogeneity of the local density of states at low energies, nanoscale inhomogeneity of the coherence peak positions and their non-uniform height. We have found that spatial variations of s-wave order parameter are positively correlated with the positions of impurities. Such behavior has been observed in scanning tunneling measurements on d-wave symmetry BSCCO-2122 superconductors.
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