The Reason why Doping Causes Superconductivity in LaFeAsO

Krüger, Ekkehard; Strunk, H. P.

doi:10.1007/s10948-012-1408-5

Cited by 4 publications

(17 citation statements)

References 32 publications

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“…1 of Ref. [7] or [8]), we find both an important difference and analogies: On the one hand, LiFeAs does not possess a magnetic band related to the space group I mma as it exists in the band structure of LaFeAsO (Sect. 2.1).…”

Section: Comparison Of the Band Structures Of Lifeas And Lafeasomentioning

confidence: 77%

“…Undoped LaFeAsO lacks a superconducting band because the two branches of any superconducting band in the space group P 4/nmm are degenerated at point M and are labeled by two representations Γ + and Γ − different with respect to the inversion [8]. Hence, the run of the bands on the lines Γ X and XM near the Fermi level of LaFeAsO and the symmetry of the Bloch functions at point Γ do not allow the construction of a superconducting band in LaFeAsO [8].…”

Section: Absence Of a Superconducting State In Undistorted Lifeasmentioning

confidence: 99%

“…Hence, the run of the bands on the lines Γ X and XM near the Fermi level of LaFeAsO and the symmetry of the Bloch functions at point Γ do not allow the construction of a superconducting band in LaFeAsO [8].…”

Section: Absence Of a Superconducting State In Undistorted Lifeasmentioning

confidence: 99%

“…The magnetic and superconducting properties of LaFeAsO have been analyzed recently on the basis of the group-theoretical nonadiabatic Heisenberg model (NHM) [7,8]. We reported evidence that both the antiferromagnetic and the superconducting state are connected with a magnetic [7,9] and a superconducting [8,10] band, respectively, of E. Krüger ( ) · H.P.…”

Section: Introductionmentioning

confidence: 99%

“…We reported evidence that both the antiferromagnetic and the superconducting state are connected with a magnetic [7,9] and a superconducting [8,10] band, respectively, of E. Krüger ( ) · H.P. Strunk Institut für Materialwissenschaft, Materialphysik, Universität Stuttgart, 70569 Stuttgart, Germany e-mail: ekkehard.krueger@imw.uni-stuttgart.de special symmetry.…”

Section: Introductionmentioning

confidence: 99%

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Structural Distortion as Prerequisite for Superconductivity in LiFeAs

Krüger

Strunk

2012

J Supercond Nov Magn

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The nonadiabatic Heisenberg model predicts a structural distortion in LiFeAs below a temperature higher than (or at least equal to) the superconducting transition temperature. Within this group-theoretical model, the reduction of the symmetry caused by the distortion is a prerequisite for the superconducting state in this compound and can be realized by a mere displacement of the iron atoms from their positions in the space group P 4/nmm.

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Section: Comparison Of the Band Structures Of Lifeas And Lafeasomentioning

confidence: 77%

Section: Absence Of a Superconducting State In Undistorted Lifeasmentioning

confidence: 99%

Section: Absence Of a Superconducting State In Undistorted Lifeasmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structural Distortion as Prerequisite for Superconductivity in LiFeAs

Krüger

Strunk

2012

J Supercond Nov Magn

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Structural Distortion in Antiferromagnetic BaFe2As2 as a Result of Time-Inversion Symmetry

Krüger

Strunk

2013

J Supercond Nov Magn

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As reported by Q. Huang et al. [Phys. Rev. Lett. 101, 257003 (2008)], neutron diffraction studies show an onset of antiferromagnetic order in BaFe2As2 associated with a tetragonal-to-orthorhombic distortion. We determine the group Cmca as the space group of antiferromagnetic BaFe2As2 and identify a roughly half-filled energy band of BaFe2As2 with Bloch functions of special symmetry as magnetic band. As explained by the group-theoretical nonadiabatic Heisenberg model, the electrons in this narrow band may lower their Coulomb correlation energy by producing just the experimentally observed antiferromagnetic state if this state does not violate group-theoretical principles. However, in undistorted BaFe2As2 the time-inversion symmetry of the system interferes with the stability of the antiferromagnetic state. Nevertheless, it can be stabilized by a structural distortion of BaFe2As2 going beyond the magnetostriction. We derive two possible structural distortions stabilizing the antiferromagnetic state. These distortions are described by their space groups and consist in mere displacements of the Fe atoms.

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Magnetotransport properties of single-crystalline LaFeAsO

et al. 2013

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Measurements of magnetization, specific heat, electrical resistivity, Hall effect, and magnetoresistance on single crystalline samples of LaFeAsO grown in a NaAs flux are reported. While this material is known to be a semimetal, the temperature dependence of the electrical resistivity data presented herein is reminiscent of semiconducting behavior and exhibits distinct features associated with a structural transition and spin density wave (SDW) order. Magnetoresistance and Hall coefficient measurements were performed in magnetic fields up to 9 T applied perpendicular to the basal plane using a van der Pauw configuration. The charge carrier density and mobility indicate that electrons are the majority charge carriers and exhibit features indicative of the structural transition and SDW formation. Low temperature X-ray diffraction measurements have confirmed that the structural transition in these samples occurs near 140 K, compared to a transition temperature of 156 K observed in polycrystalline samples. Isotherms of magnetoresistivity measured as a function of magnetic field can be scaled onto a single curve in which the scaling field is a linear function of temperature between 2.2 K and 180 K.

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The Reason why Doping Causes Superconductivity in LaFeAsO

Cited by 4 publications

References 32 publications

Structural Distortion as Prerequisite for Superconductivity in LiFeAs

Structural Distortion as Prerequisite for Superconductivity in LiFeAs

Structural Distortion in Antiferromagnetic BaFe2As2 as a Result of Time-Inversion Symmetry

Magnetotransport properties of single-crystalline LaFeAsO

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