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Shelankov, Andrei L
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Publications (10 of 23) Show all publications
Makarova, T. L., Kvyatkovskii, O. E., Zakharova, I. B., Buga, S. G., Volkov, A. P. & Shelankov, A. L. (2013). Response to "Comment on 'Laser controlled magnetism in hydrogenated fullerene films'" [J. Appl. Phys. 113, 036101 (2013)]. Journal of Applied Physics, 113(3), 036102
Open this publication in new window or tab >>Response to "Comment on 'Laser controlled magnetism in hydrogenated fullerene films'" [J. Appl. Phys. 113, 036101 (2013)]
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2013 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 113, no 3, p. 036102-Article in journal, Editorial material (Other academic) Published
National Category
Physical Sciences
Identifiers
urn:nbn:se:umu:diva-66648 (URN)000313670600079 ()
Available from: 2014-03-16 Created: 2013-02-26 Last updated: 2018-06-08Bibliographically approved
Rammer, J. & Shelankov, A. (2012). Counting quantum fluctuations of particle density. Annalen der Physik, 524(3-4), 163-174
Open this publication in new window or tab >>Counting quantum fluctuations of particle density
2012 (English)In: Annalen der Physik, ISSN 0003-3804, E-ISSN 1521-3889, Vol. 524, no 3-4, p. 163-174Article in journal (Refereed) Published
Abstract [en]

Methods of charge projectors using special gauge transformations for tagging particles are presented. Such engineering of a many-body wave function allows extracting information regarding properties of a physical system beyond average values. The method is first used to establish under which circumstances the properties of particle currents can be understood as discrete transfers of particles from one region to another. Next, the method is extended to show that in a tunnel junction coupled to a two-level system, the transmission of electrical noise causes decoherence and thereby a projective measurement of the two-level system as encoded by the amount of tunnelled charge. Finally the method is extended to deal with the exceptional circumstance where a measurement on a system with a large number of particles gives macroscopically distinguishable outcomes that are unpredictable, the observed interference pattern of interfering BEC's.

Place, publisher, year, edition, pages
Weinheim, Germany: Wiley-VCH Verlagsgesellschaft, 2012
Keywords
Quantum measurement, charge projectors, counting statistics, BEC interference
National Category
Physical Sciences
Identifiers
urn:nbn:se:umu:diva-54313 (URN)10.1002/andp.201100277 (DOI)000301772400017 ()
Available from: 2012-04-24 Created: 2012-04-24 Last updated: 2018-06-08Bibliographically approved
Makarova, T. L., Shelankov, A. L., Lyubchik, S. B., Serenkov, I. T. & Sakharov, V. I. (2012). Induced Ferromagnetism in Helium-Bombarded Graphite. Journal of Nanoscience and Nanotechnology, 12(6), 5051-5053
Open this publication in new window or tab >>Induced Ferromagnetism in Helium-Bombarded Graphite
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2012 (English)In: Journal of Nanoscience and Nanotechnology, ISSN 1533-4880, E-ISSN 1533-4899, Vol. 12, no 6, p. 5051-5053Article in journal (Refereed) Published
Abstract [en]

Irradiation with helium ions is an effective method for triggering ferromagnetism in graphite. Chemical inertness of helium suggests that local magnetic moment formation is determined solely by the intrinsic carbon defects created during the target damage. Interacting moments are located in two places: in the vicinity of the sample surface and near the point of maximum defect generation.

Place, publisher, year, edition, pages
American Scientific Publishers, 2012
Keywords
Graphite, Graphene, Carbon, Induced Ferromagnetism, Lieb's Theorem, TRIM, Irradiation
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-52102 (URN)10.1166/jnn.2012.4893 (DOI)000306861000093 ()
Available from: 2012-02-10 Created: 2012-02-10 Last updated: 2018-06-08Bibliographically approved
Makarova, T. L. L., Shelankov, A. L., Serenkov, I. T., Sakharov, V. I. & Boukhwalov, D. W. (2011). Anisotropic magnetism of graphite irradiated with medium-energy hydrogen and helium ions. Physical Review B Condensed Matter, 83(8), 085417-8 pages
Open this publication in new window or tab >>Anisotropic magnetism of graphite irradiated with medium-energy hydrogen and helium ions
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2011 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 83, no 8, p. 085417-8 pagesArticle in journal (Refereed) Published
Abstract [en]

We have studied the changes in the magnetic behavior of highly oriented pyrolytic graphite (HOPG) samples subjected to medium-energy proton and helium irradiation. The variations of the ferromagneticlike magnetization curves with the irradiation dose have been studied for two configurations: magnetic fields parallel and perpendicular to graphitic planes. For high irradiation doses, the values of magnetization at saturation are close for both geometries. At low irradiation fluences an orientationally dependent magnetic response is obtained. Directional dependence of magnetization indicates that the magnetism in irradiated graphite is triggered by vertically aligned intrinsic carbon defects induced by irradiation. This physical picture has been verified by the observation of a local stray field near linear defects by means of magnetic force microscopy. Similar results obtained with hydrogen and helium ions confirm that the chemical nature of projectiles is not crucial for formation of ferromagnetic order in oriented graphite. The dependence of induced magnetic moment versus irradiation dose shows a maximum; the optimal dose is an order of magnitude less for helium ions than for protons, being in line with simulations showing that He+ generates 8 times more defects than H+. Raman studies indicate that the degradation of magnetic ordering at large irradiation doses occurs much earlier than graphite amorphization but coincides with the destruction of graphene sheet stacking.

Place, publisher, year, edition, pages
APS Physics, 2011
Identifiers
urn:nbn:se:umu:diva-40254 (URN)10.1103/PhysRevB.83.085417 (DOI)
Available from: 2011-02-19 Created: 2011-02-19 Last updated: 2018-06-08Bibliographically approved
Makarova, T. L., Kvyatkovskii, O. E., Zakharova, I. B., Buga, S. G., Voklov, A. P. & Shelankov, A. L. (2011). Laser controlled magnetism in hydrogenated fullerene films. Journal of Applied Physics, 109(8), 083941-7
Open this publication in new window or tab >>Laser controlled magnetism in hydrogenated fullerene films
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2011 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 109, no 8, p. 083941-7Article in journal (Refereed) Published
Abstract [en]

Room temperature ferromagnetic-like behavior in fullerene photopolymerized films treated with monatomic hydrogen is reported. The hydrogen treatment controllably varies the paramagnetic spin concentration and laser induced polymerization transforms the paramagnetic phase to a ferromagnetic-like one. Excess laser irradiation destroys magnetic ordering, presumably due to structural changes, which was continuously monitored by Raman spectroscopy. We suggest an interpretation of the data based on first-principles density-functional spin-unrestricted calculations which show that the excess spin from mono-atomic hydrogen is delocalized within the host fullerene and the laser-induced polymerization promotes spin exchange interaction and spin alignment in the polymerized phase.

Place, publisher, year, edition, pages
AIP, 2011
Keywords
ab initio calculations, density functional theory, exchange interactions (electron), ferromagnetic materials, ferromagnetic-paramagnetic transitions, fullerenes, hydrogen, laser beam effects, magnetic thin films, paramagnetic materials, polymerisation, Raman spectra
Identifiers
urn:nbn:se:umu:diva-43451 (URN)10.1063/1.3581105 (DOI)
Available from: 2011-05-01 Created: 2011-05-01 Last updated: 2018-06-08Bibliographically approved
Makarova, T., Shelankov, A. L., Serenkov, I. T. & Sakharov, V. I. (2010). Magnetism in graphite induced by irradiation of hydrogen and helium atoms: a comparative study. Physica status solidi. B, Basic research, 247(11-12), 2988-2991
Open this publication in new window or tab >>Magnetism in graphite induced by irradiation of hydrogen and helium atoms: a comparative study
2010 (English)In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 247, no 11-12, p. 2988-2991Article in journal (Refereed) Published
Abstract [en]

To identify the origin of defect-induced magnetism in ion-irradiated graphite, a comparative study of samples of graphite irradiated with hydrogen H+ and helium He+ ions is performed. Directionally dependent magnetic properties, atomic/magnetic force microscopy studies suggest that the induced magnetic moments are located along the vertically aligned grain boundaries. Compared to the case of the hydrogen ion irradiation, the optimal helium irradiation dose is an order of magnitude lower. From this we conclude that the hydrogen chemistry is essentially irrelevant, and the ferromagnetic-like response of the irradiated graphite is due to structural defects regardless of their origin.

Place, publisher, year, edition, pages
Weinheim: WILEY-VCH, 2010
Keywords
graphite, helium, induced ferromagnetism, protons
Identifiers
urn:nbn:se:umu:diva-37962 (URN)10.1002/pssb.201000114 (DOI)000285798400082 ()
Available from: 2010-11-19 Created: 2010-11-19 Last updated: 2018-06-08Bibliographically approved
Gorini, C., Schwab, P., Raimondi, R. & Shelankov, A. (2010). Non-Abelian gauge fields in the gradient expansion: generalized Boltzmann and Eilenberger equations. Physical Review B Condensed Matter, 82(19), Article ID 195316.
Open this publication in new window or tab >>Non-Abelian gauge fields in the gradient expansion: generalized Boltzmann and Eilenberger equations
2010 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 82, no 19, article id 195316Article in journal (Refereed) Published
Abstract [en]

We present a microscopic derivation of the generalized Boltzmann and Eilenberger equations in the presence of non-Abelian gauges for the case of a nonrelativistic disordered Fermi gas. A unified and symmetric treatment of the charge [U(1)] and spin [SU(2)] degrees of freedom is achieved. Within this framework, just as the U(1) Lorentz force generates the Hall effect, so does its SU(2)counterpart gives rise to the spin Hall effect. Considering elastic and spin-independent disorder we obtain diffusion equations for charge and spin densities and show how the interplay between an in-plane magnetic field and a time-dependent Rashba term generates in-plane charge currents.

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-40255 (URN)10.1103/PhysRevB.82.195316 (DOI)000284205400004 ()
Available from: 2011-02-19 Created: 2011-02-19 Last updated: 2018-06-08Bibliographically approved
Makarova, T. L., Zakharova, I. B., Kvyatkovskii, O. E., Buga, S. G., Volkov, A. P. & Shelankov, A. L. (2009). Experimental realization of high spin states in dilutely hydrogenated fullerenes. Physica status solidi. B, Basic research, 246(11-12), 2778-2781
Open this publication in new window or tab >>Experimental realization of high spin states in dilutely hydrogenated fullerenes
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2009 (English)In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 246, no 11-12, p. 2778-2781Article in journal (Refereed) Published
Abstract [en]

A novel method for preparing dilutely hydrogenated fullerenes H:C60 is presented. DFT calculations of the Raman spectra at the B3LYP/3-21G level are compared with the experimental data. Under the laser treatment these phases form a rich variety of dimeric and polymeric structures, quite in contrast to pristine C60 which forms dimers and polymers bonded through the [2 + 2] addition, and in contrast to heavily hydrogenated fullerenes which do not polymerize at all. Dilutely hydrogenated fullerenes polymerize differently, forming both double bonded structures and single bonded dimers. We have shown that dilute hydrogenation of C60 creates large amount of unpaired spins which disappear due to the formation of diamagnetic single bonded dimers.

Place, publisher, year, edition, pages
John Wiley & Sons, 2009
National Category
Physical Sciences
Identifiers
urn:nbn:se:umu:diva-31892 (URN)10.1002/pssb.200982261 (DOI)
Available from: 2010-02-21 Created: 2010-02-21 Last updated: 2018-06-08Bibliographically approved
Shelankov, A. & Rammer, J. (2008). Counting statistics of interfering Bose-Einstein condensates. Europhysics letters, 83(6), 6002
Open this publication in new window or tab >>Counting statistics of interfering Bose-Einstein condensates
2008 (English)In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 83, no 6, p. 6002-Article in journal (Refereed) Published
Abstract [en]

A method is presented that is able to predict the probability of outcomes of snapshot measurements, such as the images of the instantaneous particle density distribution in a quantum many-body system. It is shown that a gauge-like transformation of the phase of the many-body wave function allows one to construct a probability generating functional, the Fourier transform of which with respect to the “gauge” field returns the joint probability distribution to detect any given number of particles at various locations. The method is applied to the problem of interference of two independent clouds of Bose-Einstein condensates, where the initially separated clouds with fixed boson numbers expand and the density profile image of the overlapping clouds is registered. In the limit of large particle numbers, the probability to observe a particular image of the density profile is shown to be given by a sum of partial probability distributions, each of which corresponds to a noisy image of interference of two matter waves with definite phase difference. In agreement with earlier theoretical arguments, interference fringes are, therefore, expected in any single shot measurement, the fringe pattern randomly varying from run to run. These results conform to the physical picture where the Bose-Einstein clouds are in spontaneously symmetry broken states, the hidden phases of which are revealed by the density profile measurement via the position of the interference fringes.

Place, publisher, year, edition, pages
EPL, 2008
Keywords
Counting statistics
National Category
Condensed Matter Physics
Research subject
Theoretical Physics
Identifiers
urn:nbn:se:umu:diva-23187 (URN)10.1209/0295-5075/83/60002 (DOI)
Available from: 2009-06-03 Created: 2009-06-03 Last updated: 2018-06-08Bibliographically approved
Wabnig, J., Rammer, J. & Shelankov, A. L. (2007). Noise spectrum of a tunnel junction coupled to a nanomechanical oscillator. Physical Review B. Condensed Matter and Materials Physics, 75(20), 205319-13 p
Open this publication in new window or tab >>Noise spectrum of a tunnel junction coupled to a nanomechanical oscillator
2007 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Physical Review B, Vol. 75, no 20, p. 205319-13 pArticle in journal (Refereed) Published
Abstract [en]

A nanomechanical resonator coupled to a tunnel junction is studied. The oscillator modulates the transmission of the junction, changing the current and the noise spectrum. The influence of the oscillator on the noise spectrum of the junction is investigated, and the noise spectrum is obtained for arbitrary frequencies, temperatures, and bias voltages. We find that the noise spectrum consists of a noise floor and a peaked structure with peaks at zero frequency, the oscillator frequency, and twice the oscillator frequency. The influence of the oscillator vanishes if the bias voltage of the junction is lower than the oscillator frequency. We demonstrate that the peak at the oscillator frequency can be used to determine the oscillator occupation number, showing that the current noise in the junction functions as a thermometer for the oscillator.

Place, publisher, year, edition, pages
AIP Physics, 2007
Keywords
noise, quantum physics, nanomechanics, electronic transport
National Category
Condensed Matter Physics Condensed Matter Physics
Research subject
Theoretical Physics
Identifiers
urn:nbn:se:umu:diva-5601 (URN)10.1103/PhysRevB.75.205319 (DOI)
Available from: 2006-12-13 Created: 2006-12-13 Last updated: 2018-06-09Bibliographically approved
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