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Publications (10 of 16) Show all publications
Nilsson, F., Karlsson, K. & Aryasetiawan, F. (2019). Dynamically screened Coulomb interaction in the parent compounds of hole-doped cuprates: Trends and exceptions. Physical Review B. Condensed Matter and Materials Physics, 99(7), 1-9, Article ID 075135.
Open this publication in new window or tab >>Dynamically screened Coulomb interaction in the parent compounds of hole-doped cuprates: Trends and exceptions
2019 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 99, no 7, p. 1-9, article id 075135Article in journal (Refereed) Published
Abstract [en]

Although cuprate high-temperature superconductors were discovered already in 1986 the origin of the pairing mechanism remains elusive. While the doped compounds are superconducting with high transition temperatures T-c, the undoped compounds are insulating due to the strong effective Coulomb interaction between the Cu 3d holes. We investigate the dependence of the maximum superconducting transition temperature T-cmax on the on-site effective Coulomb interaction U using the constrained random-phase approximation. We focus on the commonly used one-band model of the cuprates, including only the antibonding combination of the Cu d(x2-y2) and O p(x) and p(y) orbitals and find a screening-dependent trend between the static value of U and T-cmax for the parent compounds of a large number of hole-doped cuprates. Our results suggest that superconductivity may be favored by a large on-site Coulomb repulsion. We analyze both the trend in the static value of U and its frequency dependence in detail and, by comparing our results to other works, speculate on the mechanisms behind the trend.

Place, publisher, year, edition, pages
The American Physical Society, 2019
Keywords
CRYSTAL-STRUCTURE, SUPERCONDUCTIVITY, TEMPERATURE, PRESSURE
National Category
Natural Sciences Condensed Matter Physics
Research subject
Physics and Mathematics
Identifiers
urn:nbn:se:his:diva-16648 (URN)10.1103/PhysRevB.99.075135 (DOI)000459224100003 ()2-s2.0-85061980861 (Scopus ID)
Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-11-13Bibliographically approved
Sjöstrand, T. J., Karlsson, K. & Aryasetiawan, F. (2019). Influence of correlations on the orbital magnetization of the spin-1/2 Haldane-Hubbard model. Physical Review B, 100(5), 054427-1-054427-8, Article ID 054427.
Open this publication in new window or tab >>Influence of correlations on the orbital magnetization of the spin-1/2 Haldane-Hubbard model
2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, no 5, p. 054427-1-054427-8, article id 054427Article in journal (Refereed) Published
Abstract [en]

Orbital magnetization is known empirically to play an important role in several magnetic phenomena, suchas permanent magnetism and ferromagnetic superconductivity. Within the recently developed “modern theoryof orbital magnetization,” theoretical insight has been gained into the nature of this often neglected contributionto magnetism but is based on an underlying mean-field approximation. From this theory, a few treatments haveemerged which also take into account correlations beyond the mean-field approximation. Here, we apply thes cheme developed in a previous work [F. Aryasetiawan et al., Phys. Rev. B 93, 161104(R) (2016)] to thespin- 1/2 Haldane-Hubbard model to investigate the effect of charge fluctuations on the orbital magnetizationwithin the GW approximation. Qualitatively, we are led to distinguish between two quite different situations:(i) When the lattice potential is larger than the nearest-neighbor hopping, the correlations are found to boostthe orbital magnetization. (ii) If the nearest-neighbor hopping is instead larger than the lattice potential, thecorrelations reduce the magnetization. The boost and reduction are identified to stem from interband andintraband correlations, respectively, and the relative importance of the two varies with the strength of the latticepotential. We finally study graphene with parameters obtained from first principles.

Place, publisher, year, edition, pages
American Physical Society, 2019
Keywords
BERRY PHASE, REALIZATION
National Category
Condensed Matter Physics
Research subject
Physics and Mathematics
Identifiers
urn:nbn:se:his:diva-17609 (URN)10.1103/PhysRevB.100.054427 (DOI)000481815900005 ()2-s2.0-85072013362 (Scopus ID)
Available from: 2019-09-02 Created: 2019-09-02 Last updated: 2019-11-18Bibliographically approved
Aryasetiawan, F. & Karlsson, K. (2019). Modern theory of orbital magnetic moment in solids. Journal of Physics and Chemistry of Solids, 128, 87-108
Open this publication in new window or tab >>Modern theory of orbital magnetic moment in solids
2019 (English)In: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, E-ISSN 1879-2553, Vol. 128, p. 87-108Article in journal (Refereed) Published
Abstract [en]

The magnetic moment in a solid is usually associated with the electron spins but there is an additional contribution due to the orbital motion of the electrons. For a finite system such as an atom or molecule the orbital moment can be readily calculated. However, for a periodic system the formula used for finite systems becomes ill-defined due to the presence of the position operator. In the last decade a modern theory of orbital magnetization that allows for a rigorous calculation of the magnetic moment of periodic crystals has been developed. This article provides a survey of the theoretical development of this new topic as well as recent, albeit a few, applications of the new formula to real materials. Although the original theory was worked out for non-interacting systems, there has been recent progress in the theory of orbital magnetic moment of interacting electrons in solids. To include the effects of electron-electron interactions two approaches have been proposed, one based on current spin density functional theory and another on the many-body Green's function method. The two approaches are very different but both methods provide convenient yet rigorous means of including the effects of exchange and correlations beyond the commonly used local density approximation of density functional theory.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Orbital magnetism
National Category
Natural Sciences Condensed Matter Physics
Research subject
Physics and Mathematics
Identifiers
urn:nbn:se:his:diva-14610 (URN)10.1016/j.jpcs.2017.12.004 (DOI)000472693100008 ()2-s2.0-85039166407 (Scopus ID)
Funder
Carl Tryggers foundation
Available from: 2017-12-29 Created: 2017-12-29 Last updated: 2019-07-12Bibliographically approved
Kanski, J., Ilver, L., Karlsson, K., Ulfat, I., Leandersson, M., Sadowski, J. & Di Marco, I. (2017). Electronic structure of (Ga,Mn)As revisited. New Journal of Physics, 19(2), 1-8, Article ID 023006.
Open this publication in new window or tab >>Electronic structure of (Ga,Mn)As revisited
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2017 (English)In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 19, no 2, p. 1-8, article id 023006Article in journal (Refereed) Published
Abstract [en]

The detailed nature of electronic states mediating ferromagnetic coupling in dilute magnetic semiconductors, specifically (Ga,Mn)As, has been an issue of long debate. Two confronting models have been discussed emphasizing host band vs. impurity band carriers. Using angle resolved photoemission we show that the electronic structure of the (Ga,Mn)As system is significantly modified from that of GaAs throughout the valence band. Close to the Fermi energy, the presence of Mn induces a strong mixing of the bulk bands of GaAs, which results in the appearance of a highly dispersive band in the gap region of GaAs.

For Mn concentrations above 1% the band reaches the Fermi level, and can thus host the delocalized holes needed for ferromagnetic coupling. Overall, our data provide a firm evidence of delocalized carriers belonging to the modified host valence band.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2017
Keywords
Dilute magnetic semiconductors, band structure, magnetic coupling
National Category
Condensed Matter Physics
Research subject
Natural sciences; Physics and Mathematics
Identifiers
urn:nbn:se:his:diva-13328 (URN)10.1088/1367-2630/aa5a42 (DOI)000405916900002 ()2-s2.0-85014392815 (Scopus ID)
Available from: 2017-01-19 Created: 2017-01-19 Last updated: 2019-09-30Bibliographically approved
Aryasetiawan, F., Karlsson, K. & Miyake, T. (2016). Green's function theory of orbital magnetic moment of interacting electrons in solids. Physical Review B Condensed Matter, 93(16), Article ID 161104(R).
Open this publication in new window or tab >>Green's function theory of orbital magnetic moment of interacting electrons in solids
2016 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 93, no 16, article id 161104(R)Article in journal (Refereed) Published
Place, publisher, year, edition, pages
American Physical Society, 2016
National Category
Condensed Matter Physics
Research subject
Physics and Mathematics
Identifiers
urn:nbn:se:his:diva-12129 (URN)10.1103/PhysRevB.93.161104 (DOI)000373761500001 ()2-s2.0-84963767040 (Scopus ID)
Available from: 2016-04-12 Created: 2016-04-12 Last updated: 2018-11-15Bibliographically approved
Ulfat, I., Kanski, J., Ilver, L., Sadowski, J., Karlsson, K., Ernst, A. & Sandratskii, L. (2014). Effects of nonuniform Mn distribution in (Ga,Mn)As. Physical Review B Condensed Matter, 89(4), 1-5, Article ID 045312.
Open this publication in new window or tab >>Effects of nonuniform Mn distribution in (Ga,Mn)As
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2014 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 89, no 4, p. 1-5, article id 045312Article in journal (Refereed) Published
Abstract [en]

Resonant in situ photoemission from Mn 3d states in Ga(1−x)MnxAs is reported for Mn concentrations down to the very dilute level of 0.1%. Concentration-dependent spectral features are analyzed on the basis of first-principles calculations for systems with selected impurity positions as well as for random alloys. Effects of direct Mn-Mn interaction are found for concentrations as low as 2.5%, and are ascribed to statistical (nonuniform) distribution of Mn atoms.

Place, publisher, year, edition, pages
American Physical Society, 2014
National Category
Condensed Matter Physics
Research subject
Natural sciences; Mechanics of Materials
Identifiers
urn:nbn:se:his:diva-9080 (URN)10.1103/PhysRevB.89.045312 (DOI)000332298800006 ()2-s2.0-84897660307 (Scopus ID)
Available from: 2014-05-16 Created: 2014-05-16 Last updated: 2019-01-22Bibliographically approved
Di Marco, I., Thunström, P., Katsnelson, M. I., Sadowski, J., Karlsson, K., Lebegue, S., . . . Eriksson, O. (2013). Electron correlations in MnxGa1-xAs as seen by resonant electron spectroscopy and dynamical mean field theory. Nature Communications, 4, Article ID 2645.
Open this publication in new window or tab >>Electron correlations in MnxGa1-xAs as seen by resonant electron spectroscopy and dynamical mean field theory
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2013 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 4, article id 2645Article in journal (Refereed) Published
Abstract [en]

After two decades since the discovery of ferromagnetism in manganese-doped gallium arsenide, its origin is still debated, and many doubts are related to the electronic structure. Here we report an experimental and theoretical study of the valence electron spectrum of manganese-doped gallium arsenide. The experimental data are obtained through the differences between off- and on-resonance photo emission data. The theoretical spectrum is calculated by means of a combination of density-functional theory in the local density approximation and dynamical mean field theory, using exact diagonalization as impurity solver. Theory is found to accurately reproduce measured data and illustrates the importance of correlation effects. Our results demonstrate that the manganese states extend over a broad range of energy, including the top of the valence band, and that no impurity band splits-off from the valence band edge, whereas the induced holes seem located primarily around the manganese impurity.

Place, publisher, year, edition, pages
Nature Publishing Group, 2013
National Category
Condensed Matter Physics
Research subject
Natural sciences
Identifiers
urn:nbn:se:his:diva-8729 (URN)10.1038/ncomms3645 (DOI)000326472400008 ()24141268 (PubMedID)2-s2.0-84886715174 (Scopus ID)
Available from: 2014-01-07 Created: 2014-01-07 Last updated: 2017-12-06Bibliographically approved
Aryasetiawan, F., Sakuma, R. & Karlsson, K. (2012). GW approximation with self-screening correction. Physical Review B. Condensed Matter and Materials Physics, 85(3), 035106
Open this publication in new window or tab >>GW approximation with self-screening correction
2012 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 85, no 3, p. 035106-Article in journal (Refereed) Published
Abstract [en]

The GW approximation takes into account electrostatic self-interaction contained in the Hartree potential through the exchange potential. However, it has been known for a long time that the approximation contains self-screening error, as is evident in the case of the hydrogen atom. When applied to the hydrogen atom, the GW approximation does not yield the exact result for the electron removal spectra because of the presence of self-screening: the hole left behind is erroneously screened by the only electron in the system that is no longer present. We present a scheme to take into account self-screening and show that the removal of self-screening is equivalent to including exchange diagrams, as far as self-screening is concerned. The scheme is tested on a model hydrogen dimer and it is shown that the scheme yields the exact result to second order in (Uο-Uι)/2t, where Uο andare, respectively, the on-site and off-site Hubbard interaction parameters and t is the hopping parameter.

Place, publisher, year, edition, pages
American Physical Society, 2012
National Category
Physical Sciences
Research subject
Natural sciences
Identifiers
urn:nbn:se:his:diva-5917 (URN)10.1103/PhysRevB.85.035106 (DOI)000299117300003 ()2-s2.0-84856483170 (Scopus ID)
Available from: 2012-06-04 Created: 2012-06-04 Last updated: 2017-12-07Bibliographically approved
Kanski, J., Ulfat, I., Ilver, L., Leandersson, M., Sadowski, J., Karlsson, K. & Pal, P. (2012). Mn-induced modifications of Ga 3d photoemission from (Ga, Mn) As: evidence for long range effects. Journal of Physics: Condensed Matter, 24(43), Article ID 435802.
Open this publication in new window or tab >>Mn-induced modifications of Ga 3d photoemission from (Ga, Mn) As: evidence for long range effects
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2012 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 24, no 43, article id 435802Article in journal (Refereed) Published
Abstract [en]

Using synchrotron based photoemission, we have investigated the Mn-induced changes in Ga 3d core level spectra from as-grown Ga1-xMnxAs. Although Mn is located in Ga substitutional sites, and therefore does not have any Ga nearest neighbors, the impact of Mn on the Ga core level spectra is pronounced even at Mn concentrations in the region of 0.5%. The analysis shows that each Mn atom affects a volume corresponding to a sphere with around 1.4 nm diameter.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2012
National Category
Physical Sciences
Research subject
Natural sciences
Identifiers
urn:nbn:se:his:diva-6615 (URN)10.1088/0953-8984/24/43/435802 (DOI)000309965200018 ()23032788 (PubMedID)2-s2.0-84867259083 (Scopus ID)
Available from: 2012-11-12 Created: 2012-11-09 Last updated: 2017-12-07Bibliographically approved
Adell, J., Ulfat, I., Ilver, L., Sadowski, J., Karlsson, K. & Kanski, J. (2011). Thermal diffusion of Mn through GaAs overlayers on (Ga, Mn)As. Journal of Physics: Condensed Matter, 23(8), Article ID 085003.
Open this publication in new window or tab >>Thermal diffusion of Mn through GaAs overlayers on (Ga, Mn)As
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2011 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 23, no 8, article id 085003Article in journal (Refereed) Published
Abstract [en]

Thermally stimulated diffusion of Mn through thin layers of GaAs has been studied by x-ray photoemission. (Ga, Mn)As samples with 5 at% Mn were capped with 4, 6 and 8 monolayer (ML) GaAs, and Mn diffusing through the GaAs was trapped on the surface by means of amorphous As. It was found that the out-diffusion is completely suppressed for an 8 ML thick GaAs film. The short diffusion length is attributed to an electrostatic barrier formed at the (Ga, Mn)As/GaAs interface.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2011
National Category
Physical Sciences
Research subject
Natural sciences
Identifiers
urn:nbn:se:his:diva-5188 (URN)10.1088/0953-8984/23/8/085003 (DOI)000287235700006 ()2-s2.0-79951797257 (Scopus ID)
Available from: 2011-07-04 Created: 2011-07-04 Last updated: 2017-12-11Bibliographically approved
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