Effect of a nonmagnetic impurity in a nearly antiferromagnetic Fermi liquid: Magnetic correlations and transport phenomena

Kontani, Hiroshi; Ohno, M.

doi:10.1103/physrevb.74.014406

Cited by 61 publications

(72 citation statements)

References 70 publications

(222 reference statements)

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“…The formation of local moments near nonmagnetic scatterers in correlated hosts has been extensively discussed for cuprate SC. [22,24,[35][36][37][38][39] As seen from the single-impurity phase diagram in Fig. 4(b), the impurity-induced magnetization exists only in a finite wedge-shaped region in the U − V imp phase space.…”

Section: Arxiv:13102455v1 [Cond-matsupr-con] 9 Oct 2013mentioning

confidence: 99%

Impurity states and cooperative magnetic order in Fe-based superconductors

2013

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We study impurity bound states and impurity-induced order in the superconducting state of LiFeAs within a realistic five-band model based on the band structure and impurity potentials obtained from density functional theory (DFT). In agreement with recent experiments, we find that Co impurities are too weak produce sub-gap bound states, whereas stronger impurities like Cu do. We also obtain the bound state spectrum for magnetic impurities, such as Mn, and show how spin-resolved tunnelling may determine the nature of the various defect sites in iron pnictides, a prerequisite for using impurity bound states as a probe of the ground state pairing symmetry. Lastly we show how impurities pin both orbital and magnetic order, providing an explanation for a growing set of experimental evidence for unusual magnetic phases in doped iron pnictides.PACS numbers: 74.70.Xa, 74.62.En, It is crucial to understand the role of disorder in hightemperature superconductors (SC) because the materials are obtained from chemical doping with substitutional impurity atoms. In addition, through the large advance of scanning tunneling microscopy (STM), local perturbations in the host material act as nano-probes of the underlying quantum state. For the Fe-based superconductors (FeSC), a recent series of experiments have measured the local density of states (LDOS) near various impurity sites.[1] In particular, STM measurements within the SC state have focussed largely on FeSe, LiFeAs, and NaFeAs,[2-8] revealing a complex pattern of distinct impurity-induced LDOS modulations including unusual sub-gap bound states, local C 4 symmetry breaking, and generation of electronic dimers. At present no theoretical model exists which correctly captures the LDOS structure near these different impurity sites.Theoretically, both potential and magnetic point-like scatterers can generate in-gap bound states in multi-band s ± -wave SC. The single-impurity problem has been addressed both within simplified two-band models, [9][10][11][12][13][14][15] and a five-band approach, [16] reaching, however, different conclusions about the presence and location of ingap bound states. Recently, an important source of this discrepancy was shown to be the sensitivity of the low-energy states to the band structure and SC gap shape. [17,18] For modelling disorder effects in FeSC, it is therefore crucial to include the correct band structure and minimise the sensitivity of the gap structure by self-consistently calculating the SC gaps arising from this band.A final important recent development is the observation of a component of SDW order observed by e.g. muon spin rotation (µSR) experiments [19][20][21] which "cooperates" with, rather than competes with SC as is commonly assumed. This component, which exists in an intermediate doping range around optimal doping, is evidently correlated with disorder and disappears above T c . This type of disorder-induced magnetism supported by the SC state is reminiscent of that observed in underdoped cuprates where a wedge-like extension...

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Section: Arxiv:13102455v1 [Cond-matsupr-con] 9 Oct 2013mentioning

confidence: 99%

Impurity states and cooperative magnetic order in Fe-based superconductors

2013

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“…Theoretically, the slowing down and subsequent pinning of static magnetic order by disorder sites and twin boundaries, [37][38][39][40][41][42][43][44][45] and vortices [46][47][48][49][50][51][52]54 has been previously discussed extensively in the literature. From the microscopic studies, it is clear that the modulations of charge density and/or electron hopping amplitudes induced by impurities and twin boundaries can lead to local magnetic instabilities which nucleate magnetic order in the vicinity of the perturbing sites.…”

Section: Theoretical Scenariomentioning

confidence: 99%

Field-induced interplanar magnetic correlations in the high-temperature superconductorLa1.88Sr0.12CuO4

et al. 2015

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We present neutron scattering studies of the inter-planar correlations in the high-temperature superconductor La1.88Sr0.12CuO4 (Tc = 27 K). The correlations are studied both in a magnetic field applied perpendicular to the CuO2 planes, and in zero field under different cooling conditions. We find that the effect of the magnetic field is to increase the magnetic scattering signal at all values of the out-of-plane wave vector L, indicating an overall increase of the magnetic moments. In addition, weak correlations between the copper oxide planes develop in the presence of a magnetic field. This effect is not taken into account in previous reports on the field effect of magnetic scattering, since usually only L ≈ 0 is probed. Interestingly, the results of quench-cooling the sample are similar to those obtained by applying a magnetic field. Finally, a small variation of the incommensurate peak position as a function of L provides evidence that the incommensurate signal is twinned with the dominating and sub-dominant twin displaying peaks at even or odd L, respectively.

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“…However, even without SDW order, impurities can pin magnetic order locally [25][26][27] similar to what has been discussed extensively for cuprate superconductors. [42][43][44][45][46][47][48] In Fig. 1(a) we show the single impurity phase diagram at low T for impurityinduced magnetic order vs. U and V imp (below the bulk SDW phase transition at U c2…”

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Origin of electronic dimers in the spin-density wave phase of Fe-based superconductors

2014

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We investigate the emergent impurity-induced states arising from point-like scatterers in the spin-density wave phase of iron-based superconductors within a microscopic five-band model. Independent of the details of the band-structure and disorder potential, it is shown how stable magnetic (π, π) unidirectional nematogens are formed locally by the impurities. Interestingly, these nematogens exhibit a dimer structure in the electronic density, are directed along the antiferromagnetic a-axis, and have typical lengths of ∼ 10 lattice constants in excellent agreement with recent scanning tunnelling experiments. These electronic dimers provide a natural explanation of the dopant-induced transport anisotropy found e.g. in the 122 iron pnictides. [19][20][21][22][23][24]. Since impurities are known to nucleate magnetic order locally [25][26][27], it is reasonable to assume that incipient nematic order in a fluctuating state can be similarly condensed around a defect, to create a local nematic electronic state. Once present, such anisotropic defect structures can influence macroscopic anisotropy as well, and it has been suggested [3,23,28,29] that they are responsible for the resistivity anisotropy observed in detwinned Ba-122 crystals [5,6,29].Because impurities represent a well-defined perturbation which can be examined locally, studying the electronic states they create can yield important information on the background correlations present in the pure system [25]. In YBCO, for example, magnetic droplets formed around Zn impurities are known to have a size consistent with the pure antiferromagnetic (AF) correlation length.[25] At present, the microscopic mechanism responsible for the creation of local defect states in Febased materials and for breaking of rotational symmetry is unclear. Some clues are offered by STM experiments on defects in the underdoped, magnetically ordered phase, where the symmetry is already broken by the (π, 0) spindensity wave (SDW) order (the wave vector is given in the effective 1-Fe Brillouin zone). Fourier transform scanning tunneling spectroscopy (STS) deduced the existence of electronic defects with C 2 symmetry[3] nucleated by the Co dopants in Ca(Fe 1−x Co x ) 2 As 2 , while a more detailed analysis reported a dimer structure.[23] These dimers are approximately eight lattice constants (a) long and oriented along the AF a-axis, consistent with the larger resistivity found along the ferromagnetic b-axis.As a first step in understanding the origin of local C 4 symmetry breaking observed in several experiments on various materials, it seems useful to study a situation where a known chemical impurity substitutes at a known position, and ask why such a dimer-like structure (with charge or local density of states (LDOS) peaks located such a great distance from the impurity site) should be induced. As in the cuprates, this problem should be accessible to weak-coupling theories of these systems, provided they account for the electronic states of the system to which the impurity couples and tre...

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Effect of a nonmagnetic impurity in a nearly antiferromagnetic Fermi liquid: Magnetic correlations and transport phenomena

Cited by 61 publications

References 70 publications

Impurity states and cooperative magnetic order in Fe-based superconductors

Impurity states and cooperative magnetic order in Fe-based superconductors

Field-induced interplanar magnetic correlations in the high-temperature superconductorLa1.88Sr0.12CuO4

Origin of electronic dimers in the spin-density wave phase of Fe-based superconductors

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