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Lee, K.-W.; Pardo, Víctor; Pickett, Warren E.

doi:10.1103/physrevb.78.174502

Cited by 133 publications

(129 citation statements)

References 23 publications

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“…The experimentally observed nonmagnetic semiconducting character for high pressure hexagonal FeSe is therefore seen to be only consistent with an electronic system that displays substantial electronic correlations. For the tetragonal phase, our electronic structure calculations based on DFT using the LSDA are in agreement with the results of other groups [14], and inclusion of a hybrid functional does not change the calculated electronic structure of the metallic phase significantly. However, DFT+LSDA correctly reproduces the gross behavioral features of many metallic systems, even those in which electron correlations are important, such as the cuprates [26,27].…”

Section: Resultssupporting

confidence: 78%

“…We also show that unlike the iron arsenides, no static magnetic ordering is observed in β-Fe 1.01 Se at pressures up to 31 GPa. This observation is consistent with the electronic structure calculations of Lee et al, which conclude that a non magnetic ground state is most stable for iron selenide [14]. This suggests that if there is a magnetically ordered state to be found for this material, making it strictly analogous to the iron arsenide superconductors, such an ordered state is far away in temperature, pressure, and composition from what is presently known.…”

Section: Introductionsupporting

confidence: 80%

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Electronic and magnetic phase diagram of β-Fe1.01Se with superconductivity at 36.7 K under pressure

et al. 2009

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Section: Resultssupporting

confidence: 78%

Section: Introductionsupporting

confidence: 80%

Electronic and magnetic phase diagram of β-Fe1.01Se with superconductivity at 36.7 K under pressure

et al. 2009

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“…Our model contains five distinct Fe net atoms whose magnetic moments decrease with distance from the interstitial atom. Interestingly, Fe net (3) atoms that are antiferromagnetically ordered to the interstitial atom exhibit a smaller magnetic moment than Fe net (2) atoms that are ferromagnetically coupled despite equal distances from Fe int . This outcome likely stems from magnetic frustration in the model with an energetic drive to order ferromagnetically with the Fe int site.…”

Section: Magnetic Orderingmentioning

confidence: 99%

Validation of Interstitial Iron and Consequences of Nonstoichiometry in Mackinawite (Fe_1+xS)

Brgoch

Miller

2012

J. Phys. Chem. A

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A theoretical investigation of the relationship between chemical composition and electronic structure was performed on the nonstoichiometric iron sulfide, mackinawite (Fe 1+x S), which is isostructural and isoelectronic with the superconducting Fe 1+x Se and Fe 1+x (Te 1-y Se y ) phases. Even though Fe 1+x S has not been measured for superconductivity, the effects of stoichiometry on transport properties and electronic structure in all of these iron-excess chalcogenide compounds has been largely overlooked. In mackinawite, the amount of Fe that has been reported ranges from a large excess, Fe 1.15 S, to nearly stoichiometric, Fe 1.00 (7) S. Here, we analyze, for the first time, the electronic structure of Fe 1+x S to justify these nonstoichiometric phases. First principles electronic structure calculations using supercells of Fe 1+x S yield a wide range of energetically favorable compositions (0 < x < 0.30). The incorporation of interstitial Fe atoms originates from a delicate balance between the Madelung energy and the occupation of Fe-S and Fe-Fe antibonding orbitals. A theoretical assessment of various magnetic structures for "FeS" and Fe 1.06 S indicate that striped magnetic ordering along [110] is the lowest energy structure and the interstitial Fe affects the values of moments in the square planes as a function of distance. Moreover, the formation of the magnetic moment is dependent on the unit cell volume, thus relating it to composition. Finally, changes in the composition cause a modification of the Fermi surface and ultimately the loss of a nested vector. ABSTRACT: A theoretical investigation of the relationship between chemical composition and electronic structure was performed on the nonstoichiometric iron sulfide, mackinawite (Fe 1+x S), which is isostructural and isoelectronic with the superconducting Fe 1+x Se and Fe 1+x (Te 1−y Se y ) phases. Even though Fe 1+x S has not been measured for superconductivity, the effects of stoichiometry on transport properties and electronic structure in all of these iron-excess chalcogenide compounds has been largely overlooked. In mackinawite, the amount of Fe that has been reported ranges from a large excess, Fe 1.15 S, to nearly stoichiometric, Fe 1.00 (7) S. Here, we analyze, for the first time, the electronic structure of Fe 1+x S to justify these nonstoichiometric phases. First principles electronic structure calculations using supercells of Fe 1+x S yield a wide range of energetically favorable compositions (0 < x < 0.30). The incorporation of interstitial Fe atoms originates from a delicate balance between the Madelung energy and the occupation of Fe−S and Fe−Fe antibonding orbitals. A theoretical assessment of various magnetic structures for "FeS" and Fe 1.06 S indicate that striped magnetic ordering along [110] is the lowest energy structure and the interstitial Fe affects the values of moments in the square planes as a function of distance. Moreover, the formation of the magnetic moment is dependent on the unit cell volume, thus relating it to...

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“…While stoichiometric FeSe is non magnetic [10], Se-deficient superconducting samples exhibit magnetic transitions of still unknown origin [7,8]. Band structure calculations of Lee et al [11] show that Se-deficiency drives FeSe close to magnetism and short-range magnetic correlations in this material are rather strong. Recently, Imai et al [12] performed NMR measurements on Fe 1.01 Se under 2 GPa pressure and found an enhancement of antiferromagnetic spin fluctuations in parallel w i t h a r i s e o f T c .…”

Section: Introductionmentioning

confidence: 99%

Interplay between magnetism and superconductivity and the appearance of a second superconducting transition in α-FeSe at high pressure

Sidorov

Tsvyashchenko

Садыков

2009

J. Phys.: Condens. Matter

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We synthesized tetragonal a-FeSe by melting a powder mixture of iron and selenium at high pressure. Subsequent annealing at normal pressure results in removing traces of hexagonal bFeSe, formation of a rather sharp transition to superconducting state at T c ~ 7 K, and the appearance of a magnetic transition near T M = 120 K. Resistivity and ac-susceptibility were measured on the annealed sample at hydrostatic pressure up to 4.5 GPa. A magnetic transition visible in ac-susceptibility shifts down under pressure and the resistive anomaly typical for a spin density wave (SDW) antiferromagnetic transition develops near the susceptibility anomaly. T c determined by the appearance of a diamagnetic response in susceptibility, increases linearly under pressure at a rate dT c /dP = 3.5 K/GPa. Below 1.5 GPa, the resistive superconducting transition is sharp; the width of transition does not change with pressure; and, T c determined by a peak in dr/dT increases at a rate ~ 3.5 K/GPa. At higher pressure, a giant broadening of the resistive transition develops. This effect cannot be explained by possible pressure gradients in the sample and is inherent to a-FeSe. The dependences dr(T)/dT show a signature for a second peak above 3 GPa which is indicative of the appearance of another superconducting state in a-FeSe at high pressure. We argue that this second superconducting phase coexists with SDW antiferromagnetism in a partial volume fraction and originates from pairing of charge carriers from other sheets of the Fermi surface.2 Introduction Recent discovery of high T c superconductivity in layered iron arsenides [1][2][3][4] extended the family of unconventional superconductors. Previous work on high T c cuprates and heavy fermion superconductors prepared a basis for rapid progress in research on these new materials. The proximity to a magnetic instability, complex gap function, and coexistence of magnetism and superconductivity provide a key framework for future understanding the pairing mechanism of iron-based superconductors. The common structural feature of all these materials is layers composed of edge-sharing FeAs 4 -tetrahedra, separated by rare-earth-oxygen or alkaline-earth layers. The tetragonal a-phase of iron selenide has a structure composed of a stack of edge-sharing FeSe 4 -tetrahedra layer by layer, without any additional separating elements and may be regarded as an end member of a series of ironbased superconductors. Therefore, the discovery of superconductivity in a-FeSe with T c = 7 K [5] attracted considerable attention. Specific heat [5] and NMR [6] measurements indicate the unconventional nature of superconductivity in a-FeSe with lines of vanishing gap on the Fermi surface. In spite of the relatively simple structure of this binary compound, the preparation of a single phase sample is a challenge. Standard solid state reaction usually results in two or more phases in the sample, the impurity hexagonal b-phase being dominant [5][6][7][8][9]. In the first publications on superconductivity in iron seleni...

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Magnetism driven by anion vacancies in superconductingα-FeSe1−x

Cited by 133 publications

References 23 publications

Electronic and magnetic phase diagram of β-Fe1.01Se with superconductivity at 36.7 K under pressure

Electronic and magnetic phase diagram of β-Fe1.01Se with superconductivity at 36.7 K under pressure

Validation of Interstitial Iron and Consequences of Nonstoichiometry in Mackinawite (Fe_1+xS)

Interplay between magnetism and superconductivity and the appearance of a second superconducting transition in α-FeSe at high pressure

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Magnetism driven by anion vacancies in superconductingα-FeSe1−x

Cited by 133 publications

References 23 publications

Electronic and magnetic phase diagram of β-Fe1.01Se with superconductivity at 36.7 K under pressure

Electronic and magnetic phase diagram of β-Fe1.01Se with superconductivity at 36.7 K under pressure

Validation of Interstitial Iron and Consequences of Nonstoichiometry in Mackinawite (Fe1+xS)

Interplay between magnetism and superconductivity and the appearance of a second superconducting transition in α-FeSe at high pressure

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Validation of Interstitial Iron and Consequences of Nonstoichiometry in Mackinawite (Fe_1+xS)