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Andreev Reflection and Creation of Spin-Entangled Charge Carriers in Double Barrier Junctions

100%
Wojciechowski R., Kowalewski L.
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issue 2
249-253
EN
We discuss spin dependent single particle charge transport as well as the spin pairwise entanglement processes in a double barrier junction. The junction consists of a superconductor connected to two normal or spin-polarized conductors, or semiconductors. Special attention is focused on a non-local process known as a crossed Andreev reflection. The non-local Andreev reflection occurs when an incident electron (hole) from one lead, injected with a subgap energy onto a superconducting layer, transforms into an Andreev hole (electron) in the second lead. At the same time, a Cooper pair is created in the superconductor. Using the Bogolubov-de Gennes equation with appropriate boundary conditions we calculate and discuss probabilities of processes relevant for charge transport through the junction. The dependence of the tunneling charge transport on the strength and orientation of the exchange field in the ferromagnetic electrodes, and on the height of the tunnel barriers as well as on the distance between the electrodes are presented. We discuss briefly the physics of creation and charge transport of spin entangled electron-hole pairs in the junction.
2
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Spin Dependent Electron Tunneling in a Ferromagnet Superconductor Ferromagnet Junction

100%
Kowalewski L., Wojciechowski R.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
257-259
EN
The coherent spin polarized transport in ferromagnet/superconductor/ferromagnet double barrier junctions is analyzed. Using the Bogolubov-de Gennes equation with appropriate boundary conditions, we calculate probabilities of spin dependent transport processes in the ferromagnet/superconductor/ferromagnet junction. In particular, we discuss the nonlocal processes such as the crossed Andreev reflection and elastic co-tunneling. These processes contribute to tunneling a current when the distance between the two magnetic electrodes is comparable to the superconducting coherence length. The dependences of the tunneling transport processes on the strength of the exchange field in the ferromagnetic electrodes, and on the height of the tunnel barriers are presented.
3
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Josephson Effect in Graphene-Based Junctions

100%
Wojciechowski R., Kowalewski L.
Acta Physica Polonica A
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2018
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vol. 133
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issue 3
632-634
EN
We study the Josephson effect in graphene based junctions where superconductivity in graphene is induced by the proximity effect from external substrate materials. The electronic properties of the junction is described by the Dirac-Bogoliubov-de-Gennes equations. We consider the junction consisting of two superconductors with different pairing potentials. Using appropriate boundary conditions imposed on the normal region-superconductors interfaces, we calculated the Andreev bound state energy, in the ballistic limit, taking into account two types of reflections namely the retro and specular Andreev reflections.
4
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Tunneling Current into the Vortex Lattice States of s- and p-Wave Superconductors

81%
Kowalewski L., Nogala M., Thomas M., Wojciechowski R.
Acta Physica Polonica A
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2000
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vol. 97
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issue 1
237-240
EN
The tunneling current between the metallic tip of a scanning microscope and s-wave and p-wave superconductors in a quantizing magnetic field is investigated. The differential conductance is calculated both as a function of bias voltage at the centre of the vortex line and for varying position of the scanning tunneling microscope tip at a stable voltage.
5
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Heavy Fermion Superconductor Order Parameter in High Magnetic Field

81%
Kowalewski L., Wojciechowski R., Thomas M., Nogala M.
Acta Physica Polonica A
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1994
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vol. 85
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issue 2
347-350
EN
It is shown that, independently on either the nature and the strength of pairing, the orbital effects of a high magnetic field in heavy fermion superconductor change the form of both the effective pairing and the gap function.
6
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Resonance Tunneling in Ferromagnet-Triplet Superconductors Junctions

81%
Kowalewski L., Wojciechowski R., Wojtuś P.
Acta Physica Polonica A
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2007
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vol. 111
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issue 5
683-691
EN
We discuss the tunneling conductance in a ferromagnet-insulator-triplet superconductor junction. We consider the superconducting order parameters with spin triplet pairing having nodes. The nodal structure of the order parameter has been recently confirmed experimentally in Sr_2RuO_4. In particular, we study how a mid-gap structure of the tunnelling conductance depends on the phase difference of the pairing potential as well as on the orientation of the interface.
7
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Tunneling Charge Transport in Graphene-Based Superconductor Junctions

81%
Wojciechowski R., Kowalewski L., Nogala M.
Acta Physica Polonica A
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2012
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vol. 121
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issue 5-6
1092-1094
EN
We study the spin polarized electron and hole tunneling transport through a graphene-based ferromagnet(GF_1)-insulator(GI_1)-superconductor(G_{S})-insulator(GI_2)-ferromagnet(GF_2) junction. Proximity induced spin polarization and superconductivity in a graphene sheet are assumed to be created by superconducting and ferromagnetic electrodes placed on the top of the graphene. Using a four-dimensional version of the Dirac-Bogoliubov-de Gennes equation with appropriate boundary conditions we investigate the tunneling processes through the junctions. In particular, we present calculations of the amplitudes of normal and Andreev reflections as a function of the energy of the incident electron for a wide range of the model parameters, such as the strength and orientation of the exchange field, the barrier strength, and the distance between the two ferromagnetic layers. The tunneling transport processes in the graphene-based double junction GF/GI/G_{S}/GI/GF are compared with those in non-graphene-based junctions.
8
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Unconventional Superconductivity in Strong Magnetic Field

81%
Kowalewski L., Nogala M. M., Thomas M., Wojciechowski R. J.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
395-398
EN
The Landau quantization effects are considered in low carrier concentration unconventional spin triplet p-wave superconductors in a high magnetic field region. The field dependence of the superconducting order parameter and the vortex lattice states for intra Landau level pairing are analyzed. The gap functions are calculated within mean field approximation.
9
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Proceedings of the European Conference Physics of Magnetism 96. Preface.

61%
Krompiewski S., Micnas R., Fechner B., Kowalewski L., Morkowski J., Szajek A., Thomas M.
Acta Physica Polonica A
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1997
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vol. 91
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issue 1
3-6
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