Spin-density waves and itinerant antiferromagnetism in metals

Куликов, Н. И.; Tugushev, Viktor Valentinovich

doi:10.1070/pu1984v027n12abeh004088

Cited by 53 publications

(42 citation statements)

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“…It has been known from the studies of chromium and its alloys in the 70th 32,33 and from generic theoretical studies of "excitonic insulators" 34 that such nesting leads to a spin-density-wave (SDW) order with momentum Q already at weak coupling in the same way as SC order appears at weak coupling in a BCS superconductivity. For pnictides, the role of nesting for SDW order was emphasized by Cvetkovic and Tesanovic 35 and Barzykin and Gorkov 36 .…”

Section: Introductionmentioning

confidence: 99%

Renormalization group analysis of competing orders and the pairing symmetry in Fe-based superconductors

Chubukov

2009

Physica C: Superconductivity

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We analyze antiferromagnetism and superconductivity in novel F e−based superconductors within the weak-coupling, itinerant model of electron and hole pockets near (0, 0) and (π, π) in the folded Brillouin zone. We discuss the interaction Hamiltonian, the nesting, the RG flow of the couplings at energies above and below the Fermi energy, and the interplay between SDW magnetism, superconductivity and charge orbital order. We argue that SDW antiferromagnetism wins at zero doping but looses to superconductivity upon doping. We show that the most likely symmetry of the superconducting gap is A1g in the folded zone. This gap has no nodes on the Fermi surface but changes sign between hole and electron pockets. We also argue that at weak coupling, this pairing predominantly comes not from spin fluctuation exchange but from a direct pair hopping between hole and electron pockets.

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Section: Introductionmentioning

confidence: 99%

Renormalization group analysis of competing orders and the pairing symmetry in Fe-based superconductors

Chubukov

2009

Physica C: Superconductivity

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“…3a) illustrates this change even more clearly, with a very distinct kink near x = 0.22. We interpret the inflection point of T s,N (x) as a sign for a commensurate-toincommensurate transition as expected in a simple meanfield SDW picture [26][27][28]. Previously, clear evidence for incommensurability has only been reported in electron doped BaFe 2 As 2 [29][30][31].…”

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confidence: 99%

Complex phase diagram ofBa1−xNaxFe2As2: A multitude of phases striving for the electronic entropy

et al. 2016

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The low-temperature electronic phase diagram of Ba1−xNaxFe2As2, obtained using highresolution thermal-expansion and specific-heat measurements, is shown to be considerably more complex than previously reported, containing nine different phases. Besides the magnetic C2 and reentrant C4 phases, we find evidence for an additional, presumably magnetic, phase below the usual SDW transition, as well as a possible incommensurate magnetic phase. All these phases coexist and compete with superconductivity, which is particularly strongly suppressed by the C4-magnetic phase due to a strong reduction of the electronic entropy available for pairing in this phase.High-temperature superconductivity in Fe-based systems usually emerges when a stripe-type antiferromagnetic spin-density-wave (SDW) is suppressed by either doping or pressure [1][2][3]. The SDW transition is accompanied, or sometimes even slightly preceeded, by a structural phase transition from a high-temperature tetragonal (C 4 ) to a low-temperature orthorhombic (C 2 ) state, which has sparked the lively debate about electronic nematicity and the respective role of spin and orbital physics in these materials [4][5][6][7][8]. In the holedoped compounds, Ba 1−x Na x Fe 2 As 2 , Ba 1−x K x Fe 2 As 2 , and Sr 1−x Na x Fe 2 As 2 , recent studies have shown that the C 4 symmetry is restored in a small pocket within the magnetic C 2 phase region [9][10][11][12]. Mössbauer studies on Sr 0.63 Na 0.37 Fe 2 As 2 find that only half of the Fe sites carry a magnetic moment in this phase [12], which is consistent with the double-Q magnetic structure predicted within the itinerant spin-nematic scenario [6,9,12,13]. Moreover, neutron studies have shown that the spins flip from in-plane in the C 2 phase to out of plane in the C 4 reentrant phase [14], indicating that spin-orbit interactions cannot be neglected. In the Ba 1−x K x Fe 2 As 2 system, the reentrant C 4 phase reverts back to the C 2 phase near the onset of superconductivity, due to a stronger competition of the C 4 phase with superconductivity [10]. The presence of this phase in the hole-doped systems presents strong evidence that the physics of these Fe-based systems can be treated in an itinerant picture, and recent theoretical studies based upon the spin-nematic scenario can reproduce phase diagrams very similar to the experimental ones [15], as well as the spin-reorientation in the C 4 phase if spin-orbit interactions are included [16].Here, we reinvestigate in greater detail the low-temperature electronic phase diagram of Ba 1−x Na x Fe 2 As 2 using high-resolution thermalexpansion and specific-heat measurements and show that it is considerably more complex than previously * liran.wang@kit.edu † present address: The Ames Laboratory, U.S. Department of Energy, Iowa State University, Ames, Iowa 50011, USA ‡ christoph.meingast@kit.edu reported, containing nine different phases. Besides the usual C 2 and reentrant C 4 magnetic phases, we find evidence for an additional, presumably magnetic, C 2 phase, in which the orth...

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“…Secondly, in the absence of magnetic field, each eigenstate is indeed doubly degenerate, in agreement with the arguments, encapsulated in Eqn. (3). Thirdly, Eqn.…”

Section: Clues From Weak Couplingmentioning

confidence: 99%

“…Chromium crystallizes into a b.c.c. lattice, and undergoes various magnetic and structural transitions upon variation of temperature, pressure, or alloying [1][2][3].…”

Section: Chromiummentioning

confidence: 99%

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Kramers degeneracy in a magnetic field and Zeeman spin-orbit coupling in antiferromagnetic conductors

Ramazashvili

2009

Phys. Rev. B

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In this article, I analyze the symmetries and degeneracies of electron eigenstates in a commensurate collinear antiferromagnet. In a magnetic field transverse to the staggered magnetization, a hidden anti-unitary symmetry protects double degeneracy of the Bloch eigenstates at a special set of momenta. In addition to this 'Kramers degeneracy' subset, the manifold of momenta, labeling the doubly degenerate Bloch states in the Brillouin zone, may also contain an 'accidental degeneracy' subset, that is not protected by symmetry and that may change its shape under perturbation. These degeneracies give rise to a substantial momentum dependence of the transverse g-factor in the Zeeman coupling, turning the latter into a spin-orbit interaction.I discuss a number of materials, where Zeeman spin-orbit coupling is likely to be present, and outline the simplest properties and experimental consequences of this interaction, that may be relevant to systems from chromium to borocarbides, cuprates, hexaborides, iron pnictides, as well as organic and heavy fermion conductors.

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Spin-density waves and itinerant antiferromagnetism in metals

Cited by 53 publications

References 4 publications

Renormalization group analysis of competing orders and the pairing symmetry in Fe-based superconductors

Renormalization group analysis of competing orders and the pairing symmetry in Fe-based superconductors

Complex phase diagram ofBa1−xNaxFe2As2: A multitude of phases striving for the electronic entropy

Kramers degeneracy in a magnetic field and Zeeman spin-orbit coupling in antiferromagnetic conductors

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