Nearly critical spin and charge fluctuations in<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">KFe</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">As</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>observed by high-pressure NMR

Wang, P. S.; Zhou, Ping; Jia, Dongfang; Zhang, J.; Ding, Xiaxin; Lin, Hai; Wen, Hao; Normand, B.; Yu, Rong; Yu, Weiqiang

doi:10.1103/physrevb.93.085129

Cited by 20 publications

(29 citation statements)

References 56 publications

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“…An alternative scenario is that the two nematic states have different origins. In this context, recent studies of possible charge order in RbFe2As2 (36) and in KFe2As2 under high pressure (37) suggest that charge degrees of freedom could be important. Moreover, a distinguishing feature of the x = 1 compound, and of all 3d 5.5 stoichiometric compounds, is the proposed enhanced strength of electronic correlations (17)(18)(19)(20)(21)(22).…”

Section: Resultsmentioning

confidence: 99%

Novel electronic nematicity in heavily hole-doped iron pnictide superconductors

Ishida

Tsujii

Hosoi

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Electronic nematicity, a correlated state that spontaneously breaks rotational symmetry, is observed in several layered quantum materials. In contrast to their liquid-crystal counterparts, the nematic director cannot usually point in an arbitrary direction (XY nematics), but is locked by the crystal to discrete directions (Ising nematics), resulting in strongly anisotropic fluctuations above the transition. Here, we report on the observation of nearly isotropic XY-nematic fluctuations, via elastoresistance measurements, in hole-doped Ba1−xRbxFe2As2iron-based superconductors. While forx=0, the nematic director points along the in-plane diagonals of the tetragonal lattice, forx=1, it points along the horizontal and vertical axes. Remarkably, for intermediate doping, the susceptibilities of these two symmetry-irreducible nematic channels display comparable Curie–Weiss behavior, thus revealing a nearly XY-nematic state. This opens a route to assess this elusive electronic quantum liquid-crystalline state.

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Section: Resultsmentioning

confidence: 99%

Novel electronic nematicity in heavily hole-doped iron pnictide superconductors

Ishida

Tsujii

Hosoi

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…The observed d 3 + d 1 CO transition is driven by V , and is also a distinctive route from the anisotropic orbitalmultipole scattering mechanism to the valence-skipping phenomena [24]. Our study unveils another feature of the Hund's metal, and has potential implications to other multiorbital systems and observed CO in Hund's metal AFe 2 As 2 (A = Rb, K, Cs) [31][32][33]. Supplemental material for "Nonlocal Coulomb Interaction and Spin Freezing Crossover: A Route to Valence-skipping Charge Order"…”

supporting

confidence: 52%

“…The CO transition has actively been studied in the single-orbital extended Hubbard model presumably in close connection with the superconductivity of cuprates [30]. Notably, as in the case of cuprates, recent experiments reported the CO in the vicinity of the superconducting phase of AFe 2 As 2 (A = Rb, K, Cs), archetypal materials of Hund's metal [31][32][33]. Moreover, relevance of charge fluctuations or CO to the superconductivity of iron-pnictides was reported [34].…”

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confidence: 99%

Nonlocal Coulomb interaction and spin-freezing crossover as a route to valence-skipping charge order

et al. 2020

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Multiorbital systems away from global half-filling host intriguing physical properties promoted by Hund's coupling. Despite increasing awareness of this regime dubbed Hund's metal, effect of nonlocal interaction is still elusive. Here we study a three-orbital model with 1/3 filling (two electrons per site) including the intersite Coulomb interaction (V ). Using the GW plus extended dynamical mean-field theory, the valence-skipping charge order transition is shown to be driven by V . Most interestingly, the instability to this transition is significantly enhanced in the spin-freezing crossover regime, thereby lowering the critical V to the formation of charge order. This behavior is found to be closely related to the population profile of the atomic multiplet states in the spin-freezing regime. In this regime, maximum spin states are dominant in each total charge subspace with substantial amount of one-and three-electron occupations, which leads to almost equal population of one-and the maximum spin three-electron state. Our finding unveils another feature of the Hund's metal, and has potential implications to the broad range of multiorbital systems as well as the recently discovered charge order in iron-pnictides.Classifying a number of phases and understanding their relevance to different energy scales has been a central theme of condensed matter physics. In multiorbital systems away from global half-filling, Hund's coupling was shown to promote a bad metallic behavior while simultaneously pushing away the Mott insulating region [1-3]. The term Hund's metal [4,5] was coined to classify the regime in which the "Hundness" not the "Mottness" plays a leading role in determining physical properties [6,7]. The Hund's metal hosts rich phenomena such as finite temperature spin-freezing crossover [7-9], spin-orbital separation [7,10,11], anomalous transport behavior [3,4,8], increased electronic compressibility [12,13], and the orbital-differentiation [2,[14][15][16][17]. It has been believed to be one of the central doctrines to understand the intriguing physics of (mainly, but not limited to) iron-based superconductors [3-5, 12-15, 18-20] and ruthenates [3,8,21,22].In addition to the above mentioned direct manifestations of Hund's metal regime, its connection and proximity to the symmetry-broken charge-disproportionated phases has recently been highlighted [23,24]. Those which are called Hund's insulator [23] and valenceskipping phase [24-26] -a phase with two different valences while skipping the intermediate one between the two -are prominent examples. One possible route to the valence-skipping is the negative effective Coulomb repulsion, U eff < 0 [24,27,28]. Interestingly, a purely intraatomic origin, namely the anisotropic orbital-multipole scattering, was suggested to be the key ingredient for such valence-skipping phenomena [24]. Furthermore, this phase has potential implications to the electron pairing mechanisms of unconventional superconductivity [24,29].The valence-skipping compounds are prevalent in Na-tur...

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“…External pressure changes the superconducting properties of the K122 tetragonal phase. T c shows a nonmonotonic behavior on pressure [11,12,[22][23][24][25], with a minimum at p c ∼ 1.8 GPa [25]. Around this point, T c shows a universal V-shape dependence in the weak pressure regime [26], what has been reported not only in the case of K122 [25], but also for Rb122 [26] and Cs122 [27].…”

Section: Introductionmentioning

confidence: 71%

Structural, electronic, and dynamical properties of the tetragonal and collapsed tetragonal phases of KFe2As2

et al. 2019

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Compounds with a tetragonal ThCr2Si2-type structure are characterized by the possibility of the isostructural phase transition from the tetragonal phase to the collapsed tetragonal phase induced by the external pressure. An example of a compound with such a phase transition is KFe2As2, which belongs to the family of the iron-based superconductors. In this paper, we investigate the effects of the phase transition on the structural, electronic, and dynamical properties of this compound. Performing the ab initio calculations, we reproduce the dependence of the lattice constants on pressure and analyze the changes of the inter-atomic distances in the tetragonal and collapsed tetragonal phases. Using the tight binding model with maximally localized Wannier orbitals, we calculate and discuss the influence of pressure on the electronic band structure as well as on the shape of the Fermi surface. We found a precursor of the phase transition in the form of enhancement of overlapping between two Wannier orbitals of As atoms. In order to better understand the superconducting properties of KFe2As2, we study the orbital-projected Cooper pairs susceptibility as a function of pressure. We found a decrease of susceptibility with the increasing pressure in a good qualitative agreement with experimental observation. The structural transition also influences the phonon spectrum of KFe2As2, which exhibits pronounced changes induced by pressure. Some phonon modes related with the vibrations of Fe and As atoms show an anomalous, nonmonotonic dependence on pressure close to the phase transition. *

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Nearly critical spin and charge fluctuations inKFe2As2observed by high-pressure NMR

Cited by 20 publications

References 56 publications

Novel electronic nematicity in heavily hole-doped iron pnictide superconductors

Novel electronic nematicity in heavily hole-doped iron pnictide superconductors

Nonlocal Coulomb interaction and spin-freezing crossover as a route to valence-skipping charge order

Structural, electronic, and dynamical properties of the tetragonal and collapsed tetragonal phases of KFe2As2

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