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Ipp A, Leuthner M, Müller DI, Schlichting S, Singh P. Studying the 3+1D structure of the Glasma using the weak field approximation. EPJ WEB OF CONFERENCES 2022. [DOI: 10.1051/epjconf/202227405017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
We extend the weak field approximation for the Glasma beyond the boost-invariant approximation, which allows us to compute rapidity-dependent observables in the early stages of heavy-ion collisions. We show that in the limit of small fields, the weak field approximation agrees quantitatively with non-perturbative lattice simulations. Furthermore, we demonstrate that the rapidity profile of the transverse pressure is determined by longitudinal color correlations within the colliding nuclei.
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Gerasimov A, Nordström L, Khmelevskyi S, Mazurenko VV, Kvashnin YO. Nature of the magnetic moment of cobalt in ordered FeCo alloy. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:165801. [PMID: 33724237 DOI: 10.1088/1361-648x/abdfff] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 01/26/2021] [Indexed: 06/12/2023]
Abstract
The magnets are typically classified into Stoner and Heisenberg type, depending on the itinerant or localized nature of the constituent magnetic moments. In this work, we investigate theoretically the behaviour of the magnetic moments of iron and cobalt in their B2-ordered alloy. The results based on local spin density approximation for the density functional theory (DFT) suggest that the Co magnetic moment strongly depends on the directions of the surrounding magnetic moments, which usually indicates the Stoner-type mechanism of magnetism. This is consistent with the disordered local moment picture of the paramagnetic state, where the magnetic moment of cobalt gets substantially suppressed. We argue that this is due to the lack of strong on-site electron correlations, which we take into account by employing a combination of DFT and dynamical mean-field theory (DMFT). Within LDA + DMFT, we find a substantial quasiparticle mass renormalization and a non Fermi-liquid behaviour of Fe-3dorbitals. The resulting spectral functions are in very good agreement with measured spin-resolved photoemission spectra. Our results suggest that local correlations play an essential role in stabilizing a robust local moment on Co in the absence of magnetic order at high temperatures.
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Affiliation(s)
- Arsenii Gerasimov
- Theoretical Physics and Applied Mathematics Department, Ural Federal University, Mira Str. 19, 620002 Ekaterinburg, Russia
| | - Lars Nordström
- Uppsala University, Department of Physics and Astronomy, Division of Materials Theory, Box 516, SE-751 20 Uppsala, Sweden
| | - Sergii Khmelevskyi
- Center for Computational Materials Science, Institute for Applied Physics, Vienna University of Technology, Wiedner Hauptstrasse 8, A-1040, Vienna, Austria
| | - Vladimir V Mazurenko
- Theoretical Physics and Applied Mathematics Department, Ural Federal University, Mira Str. 19, 620002 Ekaterinburg, Russia
| | - Yaroslav O Kvashnin
- Uppsala University, Department of Physics and Astronomy, Division of Materials Theory, Box 516, SE-751 20 Uppsala, Sweden
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Systematic Quantum Cluster Typical Medium Method for the Study of Localization in Strongly Disordered Electronic Systems. APPLIED SCIENCES-BASEL 2018. [DOI: 10.3390/app8122401] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Great progress has been made in recent years towards understanding the properties of disordered electronic systems. In part, this is made possible by recent advances in quantum effective medium methods which enable the study of disorder and electron-electronic interactions on equal footing. They include dynamical mean-field theory and the Coherent Potential Approximation, and their cluster extension, the dynamical cluster approximation. Despite their successes, these methods do not enable the first-principles study of the strongly disordered regime, including the effects of electronic localization. The main focus of this review is the recently developed typical medium dynamical cluster approximation for disordered electronic systems. This method has been constructed to capture disorder-induced localization and is based on a mapping of a lattice onto a quantum cluster embedded in an effective typical medium, which is determined self-consistently. Unlike the average effective medium-based methods mentioned above, typical medium-based methods properly capture the states localized by disorder. The typical medium dynamical cluster approximation not only provides the proper order parameter for Anderson localized states, but it can also incorporate the full complexity of Density-Functional Theory (DFT)-derived potentials into the analysis, including the effect of multiple bands, non-local disorder, and electron-electron interactions. After a brief historical review of other numerical methods for disordered systems, we discuss coarse-graining as a unifying principle for the development of translationally invariant quantum cluster methods. Together, the Coherent Potential Approximation, the Dynamical Mean-Field Theory and the Dynamical Cluster Approximation may be viewed as a single class of approximations with a much-needed small parameter of the inverse cluster size which may be used to control the approximation. We then present an overview of various recent applications of the typical medium dynamical cluster approximation to a variety of models and systems, including single and multiband Anderson model, and models with local and off-diagonal disorder. We then present the application of the method to realistic systems in the framework of the DFT and demonstrate that the resulting method can provide a systematic first-principles method validated by experiment and capable of making experimentally relevant predictions. We also discuss the application of the typical medium dynamical cluster approximation to systems with disorder and electron-electron interactions. Most significantly, we show that in the limits of strong disorder and weak interactions treated perturbatively, that the phenomena of 3D localization, including a mobility edge, remains intact. However, the metal-insulator transition is pushed to larger disorder values by the local interactions. We also study the limits of strong disorder and strong interactions capable of producing moment formation and screening, with a non-perturbative local approximation. Here, we find that the Anderson localization quantum phase transition is accompanied by a quantum-critical fan in the energy-disorder phase diagram.
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Igarashi RN, Bezerra Neto MM, Eleno LTF, Bergman A, Klautau AB, Eriksson O, Petrilli HM. Magnetic properties of Fe(x)Co(1-x) nanochains on Pt(1 1 1) surfaces. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:206003. [PMID: 24786650 DOI: 10.1088/0953-8984/26/20/206003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The magnetic properties of FexCo1-x nanochains on Pt(1 1 1) were studied using the first-principles real-space linear muffin-tin orbital-atomic sphere approximation (RS-LMTO-ASA) method within the density functional theory. The relative amounts of Fe and Co atoms in a chosen nanochain were varied and several possible arrangements of the atomic species were taken into account. The results of the exchange interaction demonstrates ferromagnetic coupling for the nanowires. Our calculations of Fe and Co average magnetic moments reveal a large enhancement of both spin and orbital moments compared to Fe-Co films deposited on a Pt(1 1 1) surface. The trend for the orbital moments with respect to stoichiometry differs from all previous higher-dimensional Fe-Co alloys on Pt(1 1 1) studies.
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Affiliation(s)
- R N Igarashi
- Instituto de Física, Universidade de São Paulo, CP 66318, 05315-970, São Paulo-SP, Brazil
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van Dijken S, Jiang X, Parkin SSP. Nonmonotonic bias voltage dependence of the magnetocurrent in GaAs-based magnetic tunnel transistors. PHYSICAL REVIEW LETTERS 2003; 90:197203. [PMID: 12785981 DOI: 10.1103/physrevlett.90.197203] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2001] [Indexed: 05/24/2023]
Abstract
Magnetic tunnel transistors are used to study spin-dependent hot electron transport in thin CoFe films and across CoFe/GaAs interfaces. The magnetocurrent observed when the orientation of a CoFe base layer moment is reversed relative to that of a CoFe emitter, is found to exhibit a pronounced nonmonotonic variation with electron energy. A model based on spin-dependent inelastic scattering in the CoFe base layer and strong electron scattering at the CoFe/GaAs interface, resulting in a broad electron angular distribution, can well account for the variation of the magnetocurrent in magnetic tunnel transistors with GaAs(001) and GaAs(111) collectors.
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Schreiber F, Frait Z. Spin-wave resonance in high-conductivity films: The Fe-Co alloy system. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:6473-6480. [PMID: 9986666 DOI: 10.1103/physrevb.54.6473] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Abrikosov IA, James P, Eriksson O, Söderlind P, Ruban AV, Skriver HL, Johansson B. Magnetically induced crystal structure and phase stability in Fe1-cCoc. PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 54:3380-3384. [PMID: 9986237 DOI: 10.1103/physrevb.54.3380] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Hjortstam O, Trygg J, Wills JM, Johansson B, Eriksson O. Calculated spin and orbital moments in the surfaces of the 3d metals Fe, Co, and Ni and their overlayers on Cu(001). PHYSICAL REVIEW. B, CONDENSED MATTER 1996; 53:9204-9213. [PMID: 9982422 DOI: 10.1103/physrevb.53.9204] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Sorescu M, Knobbe ET. Evidence for phase selectivity in excimer-laser-induced amorphization of thermally annealed Fe66Co18B15Si glassy ferromagnet. PHYSICAL REVIEW. B, CONDENSED MATTER 1995; 52:16086-16095. [PMID: 9980991 DOI: 10.1103/physrevb.52.16086] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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Turek I, Kudrnovský J, Sob M, Drchal V, Weinberger P. Ferromagnetism of imperfect ultrathin Ru and Rh films on a Ag(001) substrate. PHYSICAL REVIEW LETTERS 1995; 74:2551-2554. [PMID: 10057956 DOI: 10.1103/physrevlett.74.2551] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Kudrnovsk J, Turek I, Pasturel A, Tetot R, Drchal V, Weinberger P. Magnetism-induced ordering in two and three dimensions. PHYSICAL REVIEW. B, CONDENSED MATTER 1994; 50:9603-9606. [PMID: 9975021 DOI: 10.1103/physrevb.50.9603] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/12/2023]
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