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1
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Analysis of the Kondo Resonance in a Single Quantum Dot Asymmetrically Coupled to Ferromagnetic Electrodes with Non-Collinear Magnetizations

100%
Wawrzyniak M.
Acta Physica Polonica A
|
2009
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vol. 115
|
issue 1
303-305
EN
The Kondo effect is studied theoretically in the framework of the non-equilibrium Green function formalism. The system under consideration consists of a single quantum dot asymmetrically coupled to ferromagnetic electrodes, whose magnetic moments are non-collinear. The spin-dependent density of states, as well as the transport characteristics such as differential conductance and tunneling magnetoresistance through the system are obtained using the equation of motion method. Numerical illustration of the mentioned quantities for several magnetic configurations and coupling strengths is presented and discussed.
2
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Poor Man's Scaling Approach to the Kondo Effect in a Single Quantum Dot Asymmetrically Attached to Ferromagnetic Leads with Non-Collinear Magnetizations

100%
Wawrzyniak M.
Acta Physica Polonica A
|
2008
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vol. 114
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issue 5
1421-1424
EN
The poor man's scaling technique is applied to the problem of electronic transport through a single quantum dot (with finite Coulomb repulsion) asymmetrically coupled to electrodes. The considered quantum dot is coupled to ferromagnetic electrodes, whose magnetic moments are non-collinear. The analysis and numerical illustration of spin splitting of the dot level as well as of the Kondo temperature on the coupling asymmetry is presented and discussed.
3
Content available remote

Correlation Histograms in Conductance Measurements of Nanowires Formed at Semiconductor Interfaces

51%
Wawrzyniak M., Martinek J., Susła B., Ilnicki G.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
384-386
EN
We demonstrate experimentally that conductance steps can occur in nanowires formed at metal-semiconductor junctions, between a cobalt tip and a germanium surface revealing long-duration plateaus at reproducible levels. The high reproducibility of the conductance traces obtained leads to very sharp peaks in the conductance histogram suggesting formation of stable atomic configurations. We develop a new type of correlation analysis of the preferred conductance values that provide new type of information on a few-atomic-nanocontact formation dynamics.
4
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Poor Man's Scaling and Green Function Analysis of the Kondo Anomaly in Single-Level Quantum Dots

51%
Wawrzyniak M., Świrkowicz R., Wilczyński M., Barnaś J.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
553-556
EN
Kondo effect in a single-level quantum dot attached to magnetic leads is studied theoretically by the "poor man's scaling" and non-equilibrium Green function methods. From the scaling equations we derive the Kondo temperature as a function of the model parameters - in particular as a function of the angle between magnetic moments. Transport characteristics, i.e. differential conductance and tunnel magnetoresistance associated with magnetization rotation, were calculated within the non-equilibrium Green function formalism based on the equation of motion method.
5
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Electronic Transport through a Quantum Dot Coupled to Non-Collinear Ferromagnetic Electrodes: The Kondo Regime

51%
Świrkowicz R., Wilczyński M., Wawrzyniak M., Barnaś J.
Acta Physica Polonica A
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2008
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vol. 113
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issue 1
565-568
EN
Linear and non-linear conductance of quantum dots attached to magnetic leads is considered theoretically in the Kondo regime. The considerations are based on the non-equilibrium Green function formalism and the relevant equation of motion method. Splitting of the Kondo anomaly due to coupling of the dot to ferromagnetic electrodes, and its dependence on magnetic configuration of the system and on the lead's spin polarization is studied numerically.
6
Content available remote

Conductance Quantization in the Melt-Spun Cubic RCu_5 (R = Gd, Ho, Lu) Nanowires

45%
Szorcz M., Susła B., Wawrzyniak M., Lipiński S., Idzikowski B.
Acta Physica Polonica A
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2009
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vol. 115
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issue 1
165-167
EN
Conductance quantization of heterocontacts between tungsten (W) tip and cubic RCu_5 (R = Gd, Ho, Lu) binary compounds prepared by melt-spinning was observed in nanowires produced dynamically using piezoelectric actuator. The conductance stepwise behaviour of the nanowires was directly observed with a storage oscilloscope. Quantum units of the nanowires conductance measured in their paramagnetic states are presented and discussed in terms of the Landauer formalism.
7
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Current-Voltage Characteristics of Nanowires Formed at the Co-Ge_{99.99}Ga_{0.01} Interface

45%
Wawrzyniak M., Maćkowski M., Śniadecki Z., Idzikowski B., Martinek J.
Acta Physica Polonica A
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2010
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vol. 118
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issue 2
375-378
EN
We present a method of measurement of the current-voltage (I-V) and conductance-voltage (G-V) characteristics of nanowires with quantum point contact formed at the Co-Ge_{99.99}Ga_{0.01} interface. The effect of the Fermi level pinning leads to the formation of an ohmic contact between Co and Ge_{99.99}Ga_{0.01}. On the measured characteristics, above the threshold value of voltage an exponential current growth is observed. Such effect could be useful in the production of the electronic nanodevices.
8
Content available remote

Spin-Dependent Phenomena in Magnetoelectronic Devices

39%
BarnaŚ J., Gmitra M., Rudziński W., Wawrzyniak M., Dugaev V., Kunert H.
Acta Physica Polonica A
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2007
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vol. 112
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issue 6
1259-1265
EN
Spin effects in electronic transport properties of artificial magnetic structures, like nanopillar spin valves, tunnel junctions, mesoscopic double-barrier junctions (single-electron transistors) are briefly discussed. Two classes of spin effects are distinguished; i.e. magnetoresistance phenomena due to magnetization rotation, and current-induced magnetic switching and magnetic dynamics.
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