Publications in 2011

1. Csaba Daday, Andrei Manolescu, D C Marinescu and Vidar Gudmundsson.
Electronic charge and spin density distribution in a quantum ring with spin-orbit and Coulomb interactions.
Phys. Rev. B 84, 115311 (September 2011).
Abstract Charge and spin density distributions are studied within a nanoring structure endowed with Rashba and Dresselhaus spin-orbit interactions (SOIs). For a small number of electrons, in the presence of an external magnetic field and of the Coulomb interaction, the energy spectrum of the system is calculated through an exact numerical diagonalization procedure. The eigenstates thus determined are used to estimate the charge and spin densities around the ring. We find that when more than two electrons are considered, the charge density deformations induced by SOIs are dramatically flattened by the Coulomb repulsion, while the spin density deformations are amplified.
URL arXiv, DOI BibTeX

@article{PhysRevB.84.115311,
title = "Electronic charge and spin density distribution in a quantum ring with spin-orbit and Coulomb interactions",
author = "Daday, Csaba and Manolescu, Andrei and Marinescu, D. C. and Gudmundsson, Vidar",
journal = "Phys. Rev. B",
volume = 84,
issue = 11,
pages = 115311,
numpages = 6,
year = 2011,
month = "Sep",
doi = "10.1103/PhysRevB.84.115311",
abstract = "Charge and spin density distributions are studied within a nanoring structure endowed with Rashba and Dresselhaus spin-orbit interactions (SOIs). For a small number of electrons, in the presence of an external magnetic field and of the Coulomb interaction, the energy spectrum of the system is calculated through an exact numerical diagonalization procedure. The eigenstates thus determined are used to estimate the charge and spin densities around the ring. We find that when more than two electrons are considered, the charge density deformations induced by SOIs are dramatically flattened by the Coulomb repulsion, while the spin density deformations are amplified.",
publisher = "American Physical Society",
arxiv = "http://arxiv.org/abs/1106.3697"
}

2. Marian Niţă, D C Marinescu, Andrei Manolescu and Vidar Gudmundsson.
Nonadiabatic generation of a pure spin current in a one-dimensional quantum ring with spin-orbit interaction.
Phys. Rev. B 83, 155427 (April 2011).
Abstract We demonstrate the theoretical possibility of obtaining a pure spin current in a 1D ring with spin-orbit interaction by irradiation with a nonadiabatic, two-component terahertz laser pulse, whose spatial asymmetry is reflected by an internal phase difference ϕ. The solutions of the equation of motion for the density operator are obtained for a spin-orbit coupling linear in the electron momentum (Rashba) and they are used to calculate the time-dependent charge and spin currents. We find that there are critical values of ϕ at which the charge current disappears, while the spin current reaches a maximum or a minimum value.
URL arXiv, DOI BibTeX

@article{PhysRevB.83.155427,
title = "Nonadiabatic generation of a pure spin current in a one-dimensional quantum ring with spin-orbit interaction",
author = "Niţă, Marian and Marinescu, D. C. and Manolescu, Andrei and Gudmundsson, Vidar",
journal = "Phys. Rev. B",
volume = 83,
issue = 15,
pages = 155427,
numpages = 5,
year = 2011,
month = "Apr",
doi = "10.1103/PhysRevB.83.155427",
abstract = "We demonstrate the theoretical possibility of obtaining a pure spin current in a 1D ring with spin-orbit interaction by irradiation with a nonadiabatic, two-component terahertz laser pulse, whose spatial asymmetry is reflected by an internal phase difference ϕ. The solutions of the equation of motion for the density operator are obtained for a spin-orbit coupling linear in the electron momentum (Rashba) and they are used to calculate the time-dependent charge and spin currents. We find that there are critical values of ϕ at which the charge current disappears, while the spin current reaches a maximum or a minimum value.",
publisher = "American Physical Society",
arxiv = "http://arxiv.org/abs/1012.4952"
}

3. Vidar Gudmundsson, Chi-Shung Tang, Cosmin Mihai Gainar, Valeriu Moldoveanu and Andrei Manolescu.
Time-dependent magnetotransport in semiconductor nanostructures via the generalized master equation.
Computer Physics Communications 182, 46 - 48 (2011).
Abstract Transport of electrons through two-dimensional semiconductor structures on the nanoscale in the presence of perpendicular magnetic field depends on the interplay of geometry of the system, the leads, and the magnetic length. We use a generalized master equation (GME) formalism to describe the transport through the system without resorting to the Markov approximation. Coupling to the leads results in elastic and inelastic processes in the system that are described to a high order by the integro-differential equation of the GME formalism. Geometrical details of systems and leads leave their fingerprints on the transport of electrons through them. The GME formalism can be used to describe both the initial transient regime immediately after the coupling of the leads to the system and the steady state achieved after a longer time.
URL arXiv, DOI BibTeX

@article{Gudmundsson201146,
title = "Time-dependent magnetotransport in semiconductor nanostructures via the generalized master equation",
journal = "Computer Physics Communications",
volume = 182,
number = 1,
pages = "46 - 48",
year = 2011,
note = "Computer Physics Communications Special Edition for Conference on Computational Physics Kaohsiung, Taiwan, Dec 15-19, 2009",
issn = "0010-4655",
doi = "10.1016/j.cpc.2010.08.006",
url = "http://www.sciencedirect.com/science/article/pii/S0010465510002961",
author = "Vidar Gudmundsson and Chi-Shung Tang and Cosmin Mihai Gainar and Valeriu Moldoveanu and Andrei Manolescu",
arxiv = "http://arxiv.org/abs/1002.1579",
abstract = "Transport of electrons through two-dimensional semiconductor structures on the nanoscale in the presence of perpendicular magnetic field depends on the interplay of geometry of the system, the leads, and the magnetic length. We use a generalized master equation (GME) formalism to describe the transport through the system without resorting to the Markov approximation. Coupling to the leads results in elastic and inelastic processes in the system that are described to a high order by the integro-differential equation of the GME formalism. Geometrical details of systems and leads leave their fingerprints on the transport of electrons through them. The GME formalism can be used to describe both the initial transient regime immediately after the coupling of the leads to the system and the steady state achieved after a longer time.",
keywords = "Generalized master equation"
}

4. Cosmin Mihai Gainar, Valeriu Moldoveanu, Andrei Manolescu and Vidar Gudmundsson.
Turnstile pumping through an open quantum wire.
New Journal of Physics 13, 013014 (2011).
Abstract We use a non-Markovian generalized master equation (GME) to describe the time-dependent charge transfer through a parabolically confined quantum wire of a finite length coupled to semi-infinite quasi-two-dimensional (2D) leads. The quantum wire and the leads are in a perpendicular external magnetic field. The contacts to the left and right leads depend on time and are kept out of phase to model a quantum turnstile of finite size. The effects of the driving period of the turnstile, the external magnetic field, the character of the contacts and the chemical potential bias on the effectiveness of the charge transfer of the turnstile are examined, in both the absence and the presence of the magnetic field. The interplay between the strength of the coupling and the strength of the magnetic field is also discussed. We observe how the edge states created in the presence of the magnetic field contribute to the pumped charge.
URL arXiv BibTeX

@article{1367-2630-13-1-013014,
author = "Cosmin Mihai Gainar and Valeriu Moldoveanu and Andrei Manolescu and Vidar Gudmundsson",
title = "Turnstile pumping through an open quantum wire",
journal = "New Journal of Physics",
volume = 13,
number = 1,
pages = 013014,
url = "http://stacks.iop.org/1367-2630/13/i=1/a=013014",
year = 2011,
arxiv = "http://arxiv.org/abs/1004.4052",
abstract = "We use a non-Markovian generalized master equation (GME) to describe the time-dependent charge transfer through a parabolically confined quantum wire of a finite length coupled to semi-infinite quasi-two-dimensional (2D) leads. The quantum wire and the leads are in a perpendicular external magnetic field. The contacts to the left and right leads depend on time and are kept out of phase to model a quantum turnstile of finite size. The effects of the driving period of the turnstile, the external magnetic field, the character of the contacts and the chemical potential bias on the effectiveness of the charge transfer of the turnstile are examined, in both the absence and the presence of the magnetic field. The interplay between the strength of the coupling and the strength of the magnetic field is also discussed. We observe how the edge states created in the presence of the magnetic field contribute to the pumped charge."
}

5. Halldor Gudfinnur Svavarsson, JaeWoong Yoon, SeokHo Song and Robert Magnusson.
Fabrication of Large Plasmonic Arrays of Gold Nanocups Using Inverse Periodic Templates.
Plasmonics 6, 741-744 (2011).
Abstract A facile procedure to fabricate large arrays of highly ordered metal nanocups, 250 nm in diameter, is reported. The nanostructure is generated from periodic photoresist templates created by holographic laser interference lithography. A subsequent gold deposition and a peeling-off step respectively results in a large area of hemispherical nano-indentations or nanocups. A wide range of coating materials can be used, and the dimensions and periodicity of the structure are easily controlled. The structure’s ability to support localized surface plasmon polaritons was manifested by reflectance spectroscopy. A good correlation between experimental data and calculated data was observed.
URL, DOI BibTeX

@article{,
year = 2011,
issn = "1557-1955",
journal = "Plasmonics",
volume = 6,
number = 4,
doi = "10.1007/s11468-011-9258-8",
title = "Fabrication of Large Plasmonic Arrays of Gold Nanocups Using Inverse Periodic Templates",
url = "http://dx.doi.org/10.1007/s11468-011-9258-8",
publisher = "Springer US",
keywords = "Nanocups; Periodic arrays; Nano-indented films; Plasmonics",
author = "Svavarsson, Halldor Gudfinnur and Yoon, JaeWoong and Song, SeokHo and Magnusson, Robert",
pages = "741-744",
abstract = "A facile procedure to fabricate large arrays of highly ordered metal nanocups, 250 nm in diameter, is reported. The nanostructure is generated from periodic photoresist templates created by holographic laser interference lithography. A subsequent gold deposition and a peeling-off step respectively results in a large area of hemispherical nano-indentations or nanocups. A wide range of coating materials can be used, and the dimensions and periodicity of the structure are easily controlled. The structure’s ability to support localized surface plasmon polaritons was manifested by reflectance spectroscopy. A good correlation between experimental data and calculated data was observed.",
language = "English"
}

6. G Mihajlović, S I Erlingsson, K Výborný, J E Pearson, S D Bader and A Hoffmann.
Magnetic-field enhancement of nonlocal spin signal in Ni80Fe20/Ag lateral spin valves.
Phys. Rev. B 84, 132407 (October 2011).
Abstract We observe a magnetic-field-induced enhancement of the nonlocal spin signal in Ni80Fe20/Ag lateral spin valves. The enhancement depends on the bias current polarity but not on the field direction. We present a theoretical model that explains our experimental results, taking into account the electron-spin relaxation of magnetic impurities. We find that the relaxation is about an order of magnitude weaker than Elliott-Yafet relaxation.
URL PDF, DOI BibTeX

@article{PhysRevB.84.132407,
title = "Magnetic-field enhancement of nonlocal spin signal in Ni80Fe20/Ag lateral spin valves",
author = "Mihajlović, G. and Erlingsson, S. I. and V\'yborn\'y, K. and Pearson, J. E. and Bader, S. D. and Hoffmann, A.",
journal = "Phys. Rev. B",
volume = 84,
issue = 13,
pages = 132407,
numpages = 4,
year = 2011,
month = "Oct",
doi = "10.1103/PhysRevB.84.132407",