Two routes to magnetic order by disorder in underdoped cuprates

Christensen, Rasmus Bjerregaard; Hirschfeld, P. J.; Andersen, Brian M.

doi:10.1103/physrevb.84.184511

Cited by 31 publications

(39 citation statements)

References 80 publications

(114 reference statements)

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“…This type of disorder-induced magnetism supported by the SC state is reminiscent of that observed in underdoped cuprates where a wedge-like extension of quasilong range antiferromagnetic (AF) order extends into the SC dome. Within the theory proposed by the present authors [22,23], this effect is caused by the coherent superposition of droplets of magnetic order which form around each impurity due to both the presence of residual AF correlations in the SC state and to the formation of bound states near the impurities.[24]Here we present a first step towards realistic theoretical modeling of impurity states in LiFeAs, including magnetic correlations, by fixing both the band and the SC pairing constants from the DFT-acquired band structure of this material. The remaining degrees of freedom are associated with the impurity potential V imp and the strength of the electronic correlations.…”

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confidence: 68%

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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confidence: 68%

Impurity states and cooperative magnetic order in Fe-based superconductors

2013

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“…Such impurities suppress SC dramatically [36]. Zinc impurities in cuprate HTSC have traditionally been treated as strong repulsive potential [37][38][39], although recent work has shown these impurities to be attractive [10,35]. We show here that for large repulsive V 0 = 7.0 (> V c ), the n imp -dependence of ∆ OP follows the weak coupling IMT behavior, rather than the strong coupling RIMT trend [49], as shown in Fig.…”

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confidence: 81%

Effects of strong disorder in strongly correlated superconductors

2017

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We investigate the effect of strong disorder on a system with strong electronic repulsion. In absence of disorder, the system has a d-wave superconducting ground-state with strong non-BCS features due to its proximity to a Mott insulator. We find that, while strong correlations make superconductivity in this system immune to weak disorder, superconductivity is destroyed efficiently when disorder strength is comparable to the effective bandwidth. The suppression of charge motion in regions of strong potential fluctuation leads to formation of Mott insulating patches, which anchor a larger non-superconducting region around them. The system thus breaks into islands of Mott insulating and superconducting regions, with Anderson insulating regions occurring along the boundary of these regions. Thus, electronic correlation and disorder, when both are strong, aid each other in destroying superconductivity, in contrast to their competition at weak disorder. Our results shed light on why Zinc impurities are efficient in destroying superconductivity in cuprates, even though it is robust to weaker impurities.Strong inter-particle interactions and strong inhomogeneous potentials both tend to localize fermions. Strong repulsion can result in complete suppression of charge motion at commensurate filling, leading to a Mott insulator [1], while strong disorder, causes decoherence of fermions triggering formation of Anderson insulators [2]. There is some evidence that weak disorder in presence of strong interactions [3][4][5][6][7] as well as strong disorder in presence of weak interactions [8] compete with each other, but the question of strong disorder in presence of strong repulsion remains unresolved. This is not merely an issue of theoretical interest, since the complex interplay of electronic interactions and disorder in twodimensional (2D) materials is often crucial to understanding novel phenomena [9][10][11][12][13][14] beyond the standard paradigm of Fermi liquid and BCS superconductivity.A prototype of strongly interacting electronic systems is the cuprate high T c superconductors (HTSC), which are antiferromagnetic Mott insulators at half-filling (one particle per site) and show d-wave superconductivity for a range of doping. In this paper, we will consider the effect of strong disorder on the strongly interacting d-wave superconducting (SC) state proximal to the Mott insulator. Our key findings are: (i) While the presence of strong correlations makes superconductivity robust to weak disorder, at large disorder comparable to bandwidth, superconductivity is rapidly suppressed. (ii) At large disorder, Mott insulating patches anchor a surrounding region akin to Anderson insulator. With increasing disorder strength, these islands grow at the expense of local superconductivity. Thus at large disorder, strong correlation and strong potential fluctuations help each other in bringing about the sudden death of superconductivity. The three distinct regions leave clear signatures in the local density of states. Our results shed ...

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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.…”

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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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Two routes to magnetic order by disorder in underdoped cuprates

Cited by 31 publications

References 80 publications

Impurity states and cooperative magnetic order in Fe-based superconductors

Impurity states and cooperative magnetic order in Fe-based superconductors

Effects of strong disorder in strongly correlated superconductors

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

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