Magnetic fluctuations in single-layer FeSe

Shishidou, Tatsuya; Agterberg, D. F.; Weinert, M.

doi:10.1038/s42005-018-0006-7

Cited by 27 publications

(23 citation statements)

References 50 publications

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“…This suggests that the relevant magnetic order does not break the translation symmetry of the lattice. DFT reveals that the only realistic possibility is fluctuations associated with CB-AFM order [21][22][23][24]. This is consistent with experiment [25,26].…”

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confidence: 87%

Resilient Nodeless d -Wave Superconductivity in Monolayer FeSe

et al. 2017

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Monolayer FeSe exhibits the highest transition temperature among the iron based superconductors and appears to be fully gapped, seemingly consistent with s-wave superconductivity. Here, we develop a theory for the superconductivity based on coupling to fluctuations of checkerboard magnetic order (which has the same translation symmetry as the lattice). The electronic states are described by a symmetry based k · p-like theory and naturally account for the states observed by angle resolved photoemission spectroscopy. We show that a prediction of this theory is that the resultant superconducting state is a fully gapped, nodeless, d-wave state. This state, which would usually have nodes, stays nodeless because, as seen experimentally, the relevant spin-orbit coupling has an energy scale smaller than the superconducting gap.The origin of superconductivity in iron based superconductors represents an important problem in condensed matter [1,2]. These materials have a relatively high superconducting transition temperature (T c ) and reveal unconventional states which are likely a consequence of electronic interactions. The most common explanation for superconductivity originates in a repulsive interaction between electron and hole pockets, leading to a superconducting gap that changes sign between these pockets [3,4]. In this context, superconductivity in single layer FeSe presents a conundrum [5,6]. Although it has the highest T c of the Fe-based superconductors, only electron pockets are present, so that the usual pairing interaction is not easily ascribable as the origin of superconductivity [5]. Furthermore, in spite of the evidence of electronic correlations in monolayer FeSe [6], the observed superconducting state is consistent with a fully gapped conventional s-wave pairing state [2,7].Understanding these apparent paradoxes is complicated by the complexity of existing theoretical models of ironbased superconductors. These models contain ten orbital and two spin degrees of freedom, which often obscures the underlying physics. Here, for monolayer FeSe, we introduce a simple symmetry-based effective k · p theory containing just two orbital degrees of freedom to describe the electronic excitations at the Fermi surface. We show that when these fermions are coupled to fluctuations associated with translation invariant checkerboard magnetic (CB-AFM) order, the resultant fully gapped, nodeless, d-wave superconducting state naturally produces the gap anisotropy seen in angle-resolved photoemission spectroscopy (ARPES) [2]. A key parameter in our k·p theory is a spin-orbit coupling (SOC) energy that is distinct from the usual on-site SOC. This SOC would usually require the nodeless d-wave state to develop nodes, but ARPES reveals this SOC is too small to allow for the nodes to develop. We then discuss how our theory generalizes to 3D K-dosed bulk FeSe and to (Li 0.8 Fe 0.2 )OHFeSe [9-11]. We do not include the role of interface phonons here but adhere to the viewpoint that these can enhance the T c found from other mechani...

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confidence: 87%

Resilient Nodeless d -Wave Superconductivity in Monolayer FeSe

et al. 2017

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“…Similar ideas were put forward independently in a description of FeSe as a paradigmatic quantum paramagnet [148]. Finally, this type of argument was also advanced in the context of the monolayer FeSe when calculating Boltzmann weighted spectra for different spiral magnetic configurations of similar energy [149].…”

Section: Long Range Ordermentioning

confidence: 86%

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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“…2(a) have the lowest degenerate energy. This suggests that there may be strong magnetic fluctuations in FeSe/LaO, which is beneficial to the emergence of superconductivity [70][71][72][73][74] .…”

Section: Results and Analysismentioning

confidence: 99%

LaO as a candidate substrate for realizing superconductivity in an FeSe epitaxial film

et al. 2021

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The significantly enhanced superconducting transition temperature (Tc) of an FeSe monolayer on SrTiO3(001) substrate has attracted extensive attention in recent years. Here, based on firstprinciples electronic structure calculations, we propose another candidate substrate LaO(001) for the epitaxial growth of FeSe monolayer to realize superconductivity. Our calculations show that for the optimal adsorption structure of FeSe monolayer on LaO(001), the stripe antiferromagnetic state and the dimer antiferromagnetic state are almost energetically degenerate, indicating the existence of strong magnetic fluctuation that is beneficial to the appearance of superconductivity. According to the Bader charge analysis, the calculated electron doping from the LaO substrate to the FeSe monolayer is about 0.18 electrons per Fe atom, even larger than that in case of FeSe/SrTiO3(001). Since LaO was also reported to be a superconductor with Tc ∼ 5 K, it may have a superconducting proximity effect on the epitaxial FeSe film and vice versa. These results suggest that LaO would be an interesting substrate to study the interface-related superconductivity.

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Magnetic fluctuations in single-layer FeSe

Cited by 27 publications

References 50 publications

Resilient Nodeless d -Wave Superconductivity in Monolayer FeSe

Resilient Nodeless d -Wave Superconductivity in Monolayer FeSe

On the Remarkable Superconductivity of FeSe and Its Close Cousins

LaO as a candidate substrate for realizing superconductivity in an FeSe epitaxial film

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