| 2111. |
- Östlin, Andreas, et al.
(författare)
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First-principles calculation of the structural stability of 6d transition metals
- 2011
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 84:11, s. 113104-
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Tidskriftsartikel (refereegranskat)abstract
- The phase stability of the 6d transition metals (elements 103-111) is investigated using first-principles electronic-structure calculations. Comparison with the lighter transition metals reveals that the structural sequence trend is broken at the end of the 6d series. To account for this anomalous behavior, the effect of relativity on the lattice stability is scrutinized, taking different approximations into consideration. It is found that the mass-velocity and Darwin terms give important contributions to the electronic structure, leading to changes in the interstitial charge density and, thus, in the structural energy difference.
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| 2112. |
- Östlin, Andreas, et al.
(författare)
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One-particle spectral function and analytic continuation for many-body implementation in the exact muffin-tin orbitals method
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 86:23, s. 235107-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate one of the most common analytic continuation techniques in condensed matter physics, namely the Pade approximant. Aspects concerning its implementation in the exact muffin-tin orbitals (EMTO) method are scrutinized with special regard towards making it stable and free of artificial defects. The electronic structure calculations are performed for solid hydrogen, and the performance of the analytical continuation is assessed by monitoring the density of states constructed directly and via the Pade approximation. We discuss the difference between the k-integrated and k-resolved analytical continuations, as well as describing the use of random numbers and pole residues to analyze the approximant. It is found that the analytic properties of the approximant can be controlled by appropriate modifications, making it a robust and reliable tool for electronic structure calculations. At the end, we propose a route to perform analytical continuation for the EMTO+dynamical mean field theory method.
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| 2113. |
- Östlund, Stellan, 1953
(författare)
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Fictitious fluxes in doped antiferromagnets
- 2002
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Ingår i: Physical Review B. - 1098-0121. ; 65
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Tidskriftsartikel (refereegranskat)abstract
- In a tight binding model of charged spin-12 electrons on a square lattice, a fully polarized ferromagnetic spin con^Lguration generates an apparent U(1) ux given by 2^Y times the skyrmion charge density of the ferromagnetic order parameter. We show here that for an antiferromagnet, there are two \^Lctitious" magnetic ^Lelds, one staggered and one unstaggered. The staggered topological ux per unit cell can be varied with a negligible change in the value of the e^Kective nearest neighbor coupling constant whereas the magnitude of the unstaggered ux is strongly coupled to the magnitude of the e^Kective coupling.
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| 2114. |
- Östlund, Stellan, 1953
(författare)
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Properties of the spin 3/2 doped Mott insulator near half filling
- 2005
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Ingår i: Physical Review B. - 1098-0121. ; 71
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Tidskriftsartikel (refereegranskat)abstract
- We develop an exact generalized Bogoliubov transformation for the spin 3/2 Hubbard model with large anti-Hunds rule coupling near half filling. Since the transformation is unitary, we can employ standard approximate mean-field theory methods in the full Hilbert space to analyze the doped Mott insulator, in contrast to a conventional approach based on truncated Hilbert spaces complemented with hard core constraints. The ground state at exactly half filling is an insulating sMottd singlet, and according to our analysis an order parameter D, usually associated with extended s-wave superconductivity, will appear self-consistently as soon as a finite density n of holes is introduced. This is a consequence of the nonlinear nature of the unitary transformation mapping the Mott singlet state to a Fock vacuum which introduces anomalous terms such as Dn in the effective Hamiltonian. Our analysis uses an approach that generalizes readily to multiband Hubbard models and could provide a mechanism whereby a superconducting order parameter proportional to density develops in Mott insulators with locally entangled ground states. For more complicated systems, such an order parameter could coexist naturally with a variety of other order parameters.
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| 2115. |
- Östlund, Stellan, 1953
(författare)
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Strong coupling Kondo lattice model as a Fermi gas
- 2007
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Ingår i: Physical Review B. - 1098-0121. ; 76
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Tidskriftsartikel (refereegranskat)abstract
- The strong coupling half-filled Kondo lattice model is an important example of a strongly interacting dense Fermi system for which conventional Fermi gas analysis has thus far failed. We remedy this by deriving an exact transformation that maps the model to a dilute gas of weakly interacting electron and hole quasiparticles that can then be analyzed by conventional dilute Fermi gas methods. The quasiparticle vacuum is a singlet Mott insulator for which the quasiparticle dynamics are simple. Since the transformation is exact, the electron spectral weight sum rules are obeyed exactly. Subtleties in the behavior of electrons in the singlet Mott insulator can be reduced to a complicated but precise relation between quasiparticles and bare electrons. The theory of free quasiparticles can also be interpreted as an exactly solvable model for a singlet Mott insulator, providing an exact model in which to explore the strong coupling regime of a singlet Kondo insulator.
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| 2116. |
- Molin, M., et al.
(författare)
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Case management at an outpatient unit for severe and enduring eating disorder patients at Stockholm Centre for Eating Disorders : a study protocol
- 2016
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Ingår i: International Journal of Eating Disorders. - London, United Kingdom : BioMed Central. - 0276-3478 .- 1098-108X .- 2050-2974. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Background: Patients with severe and enduring eating disorders (SEED) are seriously ill and have a low quality of life. Case management (CM), originally developed for adult patients with severe mental disabilities, has been shown to enhance social functioning and improve quality of life, while reducing the number and length of hospitalizations. In 2014, a special unit based on CM, for patients with SEED (the Eira unit) was started at Stockholm Centre for Eating Disorders, Sweden.Method/Design: This study aims to investigate if CM can improve SEED patients' quality of life, and reduce their eating disorder symptoms as well as their health care consumption. Methods for data collection are a semi-structured diagnostic interview, self-report questionnaires, and a qualitative interview. The diagnostic interview and the self-report assessments will be done at start of treatment and at follow-ups after 1, 2, and 3years. The qualitative interview will be conducted 1 year after start of treatment. The study is approved by the ethical review board in Stockholm in compliance with the Helsinki Declaration.Discussion: CM is a possible new contribution to the treatment methods for SEED. It does not aim at remission, but rather to accept life as it is, and to enhance quality of life in the presence of the ED. This study will investigate the potential benefits of this novel intervention in a special unit for SEED patients.Trail Registration: Clinicaltrials.gov Id: NCT02897622.
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