Iron Isotope Effect and Local Lattice Dynamics in the (Ba, K)Fe2As2 Superconductor Studied by Temperature-Dependent EXAFS

Chu, Wei; Cheng, Jie; Chu, Shengqi; Hu, Tiandou; Marcelli, A.; Chen, Xianhui; Zhang, Wu

doi:10.1038/srep01750

Cited by 31 publications

(22 citation statements)

References 28 publications

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“…51 We introduced the isotope coefficient (α ω ) using the phonon frequency as the phonon frequency is intimately related to the Einstein temperature via effective force constant k 0 ∝ ω 2 so T E ∝ ω. Therefore, α ω may be defined as − M ∆M ∆ω ω , where ∆ω is the change in phonon frequency upon isotope substitution and M is the atomic mass of the isotope substituted.…”

Section: Resultsmentioning

confidence: 99%

“…In fact, the electronphonon strength in FeBS is compared to that in MgBr 2 superconductor, where the superconductivity is mediated by electron-phonon coupling. In addition to these theoretical calculations, a large isotope coefficient as high as α Fe ∼ 0.81 has been reported experimentally for different families of FeBS, [46][47][48][49][50][51][52] clearly suggesting that the electron-phonon coupling can not be ruled out in understanding the pairing mechanism in these materials along with other degrees of freedom such as spin and orbital.…”

Section: Introductionmentioning

confidence: 89%

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Iron isotope effect in SmFeAsO0.65 and SmFeAsO0.77H0.12 superconductors: A Raman study

et al. 2016

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We report the inelastic light scattering studies on SmFeAsO0.65 and SmFeAsO0.77H0.12 with iron isotopes namely 54Fe and 57Fe. In both of these systems under investigation we observed a significant shift in the frequency of the phonon modes associated with the displacement of Fe atoms around ∼ 200 cm-1. The observed shift in the Fe mode (B1g) for SmFeAsO0.65 is ∼ 1.4 % and lower in case of SmFeAsO0.77H0.12, which is ∼ 0.65 %, attributed to the lower percentage of isotopic substitution in case of SmFeAsO0.77H0.12. Our study reveals the significant iron isotope effect in these systems hinting towards the crucial role of electron-phonon coupling in the pairing mechanism of iron based superconductors.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 89%

Iron isotope effect in SmFeAsO0.65 and SmFeAsO0.77H0.12 superconductors: A Raman study

et al. 2016

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“…The role of lattice vibrations in the mechanism of SC in unconventional superconductors is still controversial. The observation of strong electron-phonon and spin-phonon coupling, both in cuprates [32][33][34][35] and iron superconductors [36][37][38][39][40][41] indicates that the electron-phonon coupling (EPC) may play an important role in the unconventional superconductors, at least to explain the observed Fe-isotope effect [42], the anomalous temperature dependence of the local Fe-As displacement [43], gap anisotropy, and the correlation of T c with the Fe-anion height [44]. These observations also suggest polaron and/or bipolaron driven superconductivity in this material [45][46][47][48][49][50].…”

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confidence: 99%

Strong pressure-dependent electron-phonon coupling in FeSe

2014

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We have computed the correlated electronic structure of FeSe and its dependence on the A 1g mode versus compression. Using the self-consistent density functional theory -dynamical mean field theory (DFT-DMFT) with continuous time quantum Monte Carlo (CTQMC), we find that there is greatly enhanced coupling between some correlated electron states and the A 1g lattice distortion. Superconductivity in FeSe shows a very strong sensitivity to pressure, with an increase in Tc of almost a factor of 5 within a few GPa, followed by a drop, despite monotonic pressure dependence of almost all electronic properties. We find that the maximum A 1g deformation potential behaves similar to the experimental Tc. In contrast, the maximum deformation potential in DFT for this mode increases monotonically with increasing pressure.PACS numbers: 74.70. Xa, 74.25.Jb, 75.10.Lp So far there is no predictive theory for superconductivity in the cuprate and iron-superconductors, hence these superconductors can be classified as non-conventional superconductors, since there is a well-developed, predictive theory for electron-phonon superconductors whose normal state is well-represented by conventional density functional theory (DFT) [1][2][3]. The unconventional superconductors are very sensitive to applied pressure, so pressure provides a control to test theories and develop a better understanding [4][5][6]. Here we study superconductivity under applied pressure in pure FeSe; unlike cuprates, superconductivity in FeSe arises without doping. FeSe is an ideal system to study the electron pairing mechanism due to the simplicity of its crystal and electronic structure. It shows a very strong enhancement of T c upon application of modest pressure with dramatic increase of T c from 8K to ∼ 37K [4,7,8] and then decreases upon further application of pressure. Why does T c increase with pressure and then decrease for rather small lattice compression? This question was addressed in Ref. 8, where it was found that applied pressure (P) intensified antiferromagnetic spin fluctuations (SF). However, this did not explain the decrease in T c with further compression.The discovery of the iron superconductors showed that high T c is not specific to the cuprates, and suggests a wider field of potential high T c materials [9]. Although DFT gives many properties reasonably accurately for both cuprates [10][11][12] and Fe-superconductors [13][14][15], there is also significant indication of the importance of correlations and fluctuating local moments beyond DFT specially for the Fe-superconductors which are paramagnetic metals in room temperature, and Dynamical Mean Field Theory (DMFT) has proved to be a good approximation [16][17][18][19][20][21][22].While most studies suggest a spin fluctuation coupling mechanism for SC in Fe-superconductors similarly to cuprates [23][24][25], strong coupling phonons have also been proposed to play a role in both sets of materials [3,[26][27][28][29][30]. The study of strong electron-phonon coupling in correlated solids is in...

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“…Bulk probes used to characterise iron-based superconductors include standard SQUID magnetometry, X-ray diffraction (XRD) [17], X-ray Absorption Spectroscopy (XANES [18,19], EXFAS [20,21]), neutron scattering [22][23][24], Muon-spin rotation [25,26], Nuclear Magnetic Resonance (NMR) [27] and Mössbauer Spectroscopy [28]. In addition, Angle-resolved Photoelectron Spectroscopy (ARPES), a surface sensitive synchrotron technique, is increasingly employed for measuring the band-structure of occupied electronic states in the vicinity of the Fermi level [29][30][31][32].…”

Section: Overview Of Characterisation Techniquesmentioning

confidence: 99%

Analytical microscopy of iron-based superconducting materials

Speller¹,

Mousavi²,

Dudin³

2015

Novel Superconducting Materials

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Inhomogeneity and phase separation in unconventional superconducting materials is a topic of increasing interest, as the competition between phases with different types of ordering is thought to play an important role in the emergence of the high temperature superconducting state. A wide range of experimental techniques are available for investigating the crystallography of these complex materials, however the majority are bulk probes. Here we briefly review some spatially resolved techniques that are being used to investigate phase separation in ironbased superconductors, with a focus on analytic Scanning Electron Microscopy techniques and synchrotron-based Photoelectron Microscopy.

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Iron Isotope Effect and Local Lattice Dynamics in the (Ba, K)Fe2As2 Superconductor Studied by Temperature-Dependent EXAFS

Cited by 31 publications

References 28 publications

Iron isotope effect in SmFeAsO0.65 and SmFeAsO0.77H0.12 superconductors: A Raman study

Iron isotope effect in SmFeAsO0.65 and SmFeAsO0.77H0.12 superconductors: A Raman study

Strong pressure-dependent electron-phonon coupling in FeSe

Analytical microscopy of iron-based superconducting materials

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