Nature of magnetic excitations in superconducting BaFe1.9Ni0.1As2

Liu, Mengshu; Harriger, Leland; Luo, Huiqian; Wang, Meng; Ewings, R. A.; Guidi, T.; Park, Hyowon; Haule, Kristjan; Kotliar, Gabriel; Hayden, Stephen M; Dai, Pengcheng

doi:10.1038/nphys2268

Cited by 151 publications

(284 citation statements)

References 31 publications

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“…Since single crystals of electron and hole-doped BaFe 2 As 2 are available, one can systematically map out the evolution of spin excitations at different electron/hole-doping levels marked with arrows in the phase diagram [ Fig. 18(a)] Harriger et al, 2011;Lee et al, 2011;Liu et al, 2012a;Luo et al, 2013a;Tucker et al, 2012a;Wang et al, 2013b). The solid lines in Figs.…”

Section: B Neutron Spin Resonance and Its Relationship With Superconmentioning

confidence: 99%

Antiferromagnetic order and spin dynamics in iron-based superconductors

2015

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High-transition temperature (high-Tc) superconductivity in the iron pnictides/chalcogenides emerges from the suppression of the static antiferromagnetic order in their parent compounds, similar to copper oxides superconductors. This raises a fundamental question concerning the role of magnetism in the superconductivity of these materials. Neutron scattering, a powerful probe to study the magnetic order and spin dynamics, plays an essential role in determining the relationship between magnetism and superconductivity in high-Tc superconductors. The rapid development of modern neutron time-of-flight spectrometers allows a direct determination of the spin dynamical properties of iron-based superconductors throughout the entire Brillouin zone. In this review, we present an overview of the neutron scattering results on iron-based superconductors, focusing on the evolution of spin excitation spectra as a function of electron/hole-doping and isoelectronic substitution. We compare spin dynamical properties of iron-based superconductors with those of copper oxide and heavy fermion superconductors, and discuss the common features of spin excitations in these three families of unconventional superconductors and their relationship with superconductivity.

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Section: B Neutron Spin Resonance and Its Relationship With Superconmentioning

confidence: 99%

Antiferromagnetic order and spin dynamics in iron-based superconductors

2015

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“…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].…”

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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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“…DFT in combination with dynamical mean field theory (DMFT) (DFT+DMFT) has proved to be a good approximation to describe fluctuating local moment and electron correlation 22,23 . The structures and the atom positions used here are taken from the neutron scattering measurement 15 .…”

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confidence: 99%

Pressure suppression of electron correlation in the collapsed tetragonal phase ofCaFe2As2: A DFT-DMFT investigation

2014

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Recent studies reveal a pressure induced transition from a paramagnetic tetragonal phase (T) to a collapsed tetragonal phase (CT) in CaF e 2 As 2 , which was found to be superconducting with non-hydrostatic pressure at low temperature. We have investigated the effects of electron correlation and local fluctuating moment in both tetragonal and collapsed tetragonal phases of the paramagnetic CaF e 2 As 2 using self consistent DFT+DMFT with continuous time quantum Monte Carlo as the impurity solver. From the computed optical conductivity, we find a gain in the optical kinetic energy due to the loss in Hund's rule coupling energy in the CT. We find that the transition from T to CT turns CaF e 2 As 2 from a bad metal into a good metal. Computed mass enhancement and local moments also show significant decrease in the CT, which confirms the suppression of the electron correlation in CT phase of CaF e 2 As 2 .

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Nature of magnetic excitations in superconducting BaFe1.9Ni0.1As2

Cited by 151 publications

References 31 publications

Antiferromagnetic order and spin dynamics in iron-based superconductors

Antiferromagnetic order and spin dynamics in iron-based superconductors

Strong pressure-dependent electron-phonon coupling in FeSe

Pressure suppression of electron correlation in the collapsed tetragonal phase ofCaFe2As2: A DFT-DMFT investigation

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