Theoretical study of impurity-induced magnetism in FeSe

Martiny, Johannes H. J.; Kreisel, Andreas; Andersen, Brian M.

doi:10.1103/physrevb.99.014509

Cited by 22 publications

(18 citation statements)

References 67 publications

(96 reference statements)

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“…Recently, a scanning tunneling microscopy (STM) study observed a signature of local spin fluctuations near the Fe defect in multi-layer FeSe on SrTiO3 substrate [17]. Such magnetic instability, as pointed out in recent theory papers, suggests the possibility that the magnetism can be triggered by impurities in FeSe [18,19].…”

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confidence: 86%

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Visualization of Local Magnetic Moments Emerging from Impurities in Hund’s Metal States of FeSe

et al. 2020

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Understanding the origin of the magnetism of high temperature superconductors is crucial for establishing their unconventional pairing mechanism. Recently, theory predicts that FeSe is close to a magnetic quantum critical point, and thus weak perturbations such as impurities could induce local magnetic moments. To elucidate such quantum instability, we have employed scanning tunneling microscopy and spectroscopy. In particular, we have grown FeSe film on superconducting Pb(111) using molecular beam epitaxy and investigated magnetic excitation caused by impurities in the proximity-induced superconducting gap of FeSe. Our study provides a deep insight into the origin of the magnetic ordering of FeSe by showing the way local magnetic moments develop in response to impurities near the magnetic quantum critical point.

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confidence: 86%

“…4d-f) are not symmetric under the mirror operation [17,42]. Recent theory shows that orbital-selectivity can give rise to chiral patterns in the conductance maps from local magnetic ordering near Fe defects, upon which the mirror symmetry is broken [19].…”

Section: Supplemental Material)mentioning

confidence: 99%

Visualization of Local Magnetic Moments Emerging from Impurities in Hund’s Metal States of FeSe

et al. 2020

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“…Within experimental resolution, the peak was found to remain centered at zero bias as a function of both STM tip position and application of c-axis applied magnetic fields up to 8 T. Furthermore, it was measured to extend uniformly in space with a length scale of order 3-4 Å, and decrease in amplitude (but not split) when proximate to other impurity bound states [361]. These peculiar properties are not characteristics of standard in-gap bound states of FeSCs arising from magnetic or nonmagnetic impurities [393][394][395][396][397]. Intriguingly, similar robust zero-energy conductance peaks have been recently detected near Fe adatoms, deposited on top of the stoichiometric materials LiFeAs and PbTaSe 2 [398], and on monolayers of FeSe/STO and FeTe 0.5 Se 0.5 /STO [399].…”

Section: Experimental Evidence For Majorana Zero Modes: Defect Statesmentioning

confidence: 98%

On the Remarkable Superconductivity of FeSe and Its Close Cousins

2020

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Emergent electronic phenomena in iron-based superconductors have been at the forefront of condensed matter physics for more than a decade. Much has been learned about the origins and intertwined roles of ordered phases, including nematicity, magnetism, and superconductivity, in this fascinating class of materials. In recent years, focus has been centered on the peculiar and highly unusual properties of FeSe and its close cousins. This family of materials has attracted considerable attention due to the discovery of unexpected superconducting gap structures, a wide range of superconducting critical temperatures, and evidence for nontrivial band topology, including associated spin-helical surface states and vortex-induced Majorana bound states. Here, we review superconductivity in iron chalcogenide superconductors, including bulk FeSe, doped bulk FeSe, FeTe1−xSex, intercalated FeSe materials, and monolayer FeSe and FeTe1−xSex on SrTiO3. We focus on the superconducting properties, including a survey of the relevant experimental studies, and a discussion of the different proposed theoretical pairing scenarios. In the last part of the paper, we review the growing recent evidence for nontrivial topological effects in FeSe-related materials, focusing again on interesting implications for superconductivity.

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“…3a, b, exerts a serious problem for the "plain vanilla" RPA approach that cannot be alleviated by a small change of parameters, see Supplementary Note 1. However, certainly for FeSe it is well known that additional electronic interaction effects are required to explain, for example, the energy and momentum dependence of the magnetic fluctuations, or the superconducting pairing kernel 33,36,37,40,71 . Indeed, FeSe has been advocated to be an example of a Hund's metal where sizable orbital decoupling takes place as a consequence of large Hubbard-Hund interactions 37,[72][73][74] .…”

Section: Principle Of the Experimentsmentioning

confidence: 99%

Singular magnetic anisotropy in the nematic phase of FeSe

et al. 2020

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FeSe is arguably the simplest, yet the most enigmatic, iron-based superconductor. Its nematic but non-magnetic ground state is unprecedented in this class of materials and stands out as a current puzzle. Here, our nuclear magnetic resonance measurements in the nematic state of mechanically detwinned FeSe reveal that both the Knight-shift and the spin–lattice relaxation rate 1/T1 possess an in-plane anisotropy opposite to that of the iron pnictides LaFeAsO and BaFe2As2. Using a microscopic electron model that includes spin–orbit coupling, our calculations show that an opposite quasiparticle weight ratio between the dxz and dyz orbitals leads to an opposite anisotropy of the orbital magnetic susceptibility, which explains our Knight-shift results. We attribute this property to a different nature of nematic order in the two compounds, predominantly bond type in FeSe and onsite ferro-orbital in pnictides. The T1 anisotropy is found to be inconsistent with existing neutron scattering data in FeSe, showing that the spin fluctuation spectrum reveals surprises at low energy, possibly from fluctuations that do not break C4 symmetry. Therefore, our results reveal that important information is hidden in these anisotropies and they place stringent constraints on the low-energy spin correlations as well as on the nature of nematicity in FeSe.

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Theoretical study of impurity-induced magnetism in FeSe

Cited by 22 publications

References 67 publications

Visualization of Local Magnetic Moments Emerging from Impurities in Hund’s Metal States of FeSe

Visualization of Local Magnetic Moments Emerging from Impurities in Hund’s Metal States of FeSe

On the Remarkable Superconductivity of FeSe and Its Close Cousins

Singular magnetic anisotropy in the nematic phase of FeSe

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