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1
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Aharonov-Bohm and Relativistic Corbino Effects in Graphene: A Comparative Study of Two Quantum Interference Phenomena

100%
Rycerz A.
Acta Physica Polonica A
|
2012
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vol. 121
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issue 5-6
1242-1245
EN
This is an analytical study of magnetic fields effects on the conductance, the shot noise power, and the third charge-transfer cumulant for the Aharonov-Bohm rings and the Corbino disks in graphene. The two distinct physical mechanisms lead to very similar magnetotransport behaviors. Differences are unveiled when discussing the third-cumulant dependence on magnetic fields.
2
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Aharonov-Bohm Effect and Valley Polarization in Nanoscopic Graphene Rings

100%
Rycerz A.
Acta Physica Polonica A
|
2009
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vol. 115
|
issue 1
322-325
EN
The conductance of an Aharonov-Bohm interferometer is studied in a tight-binding model of graphene. Two point contacts with zigzag edges, which function as valley filters, are connected by a ring with an irregular boundary. We find that the narrowest rings show strong current suppression and nearly sinusoidal magnetoconductance oscillations, whereas for wide rings higher harmonics are equally represented. In the intermediate width range, oscillations with a basic periodicity are suppressed when two valley filters have opposite polarity, while higher harmonics are unaffected. The effect is interpreted in terms of a relatively weak intervalley scattering in the system.
3
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Electron Transport and Quantum-Dot Energy Levels in Z-Shaped Graphene Nanoconstriction with Zigzag Edges

100%
Rycerz A.
|
|
issue 2
238-243
EN
Motivated by recent advances in fabricating graphene nanostructures, we find that an electron can be trapped in Z-shaped graphene nanoconstriction with zigzag edges. The central section of the constriction operates as a single-level quantum dot, as the current flow towards the adjunct sections (rotated by 60°) is strongly suppressed due to mismatched valley polarization, although each section in isolation shows maximal quantum value of the conductance G_0 = 2e^2/h. We further show that the trapping mechanism is insensitive to the details of constriction geometry, except from the case when widths of the two neighboring sections are equal. The relation with earlier studies of electron transport through symmetric and asymmetric kinks with zigzag edges is also established.
4
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Josephson Network as a Model for Inhomogeneous Superconductor: a Microwave Power Absorption

63%
Rycerz A., Spałek J.
Acta Physica Polonica A
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2007
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vol. 111
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issue 4
581-594
EN
We discuss the applied magnetic field dependence of the microwave absorption by a three-dimensional array of up to 30×30 ×30 Josephson junctions with random parameters including the resistivity, capacity, and inductance of each junction. The numerical simulation results for the networks show characteristic microwave absorption anomalies observed in the ceramic samples of high temperature superconductor YBa_2Cu_3O_{7-x}. We also provide a discussion of the absorption in simple analytical terms of the Josephson loop instabilities.
5
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Conditions for Conductance Quantization in Mesoscopic Dirac Systems on the Examples of Graphene Nanoconstrictions

63%
Rut G., Rycerz A.
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|
vol. 126
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issue 4a
A-114-A-118
EN
Ballistic transport through an impurity-free section of the Corbino disk in graphene is investigated by means of the Landauer-Büttiker formalism in the mesoscopic limit. In the linear-response regime the conductance is quantized in steps close to integer multiples of 4e²/h, yet Fabry-Perot oscillations are strongly suppressed. The quantization arises for small opening angles θ ≲ π/3 and large radii ratios R_2/R_1 ≳ 10. We find that the condition for emergence of the n-th conductance step can be written as √nθ/π ≪ 1. A brief comparison with the conductance spectra of graphene nanoribbons with parallel edges is also provided.
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