Neutron-Scattering Measurements of Spin Excitations in LaFeAsO and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mi>Ba</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:msub><mml:mrow><mml:mi>Fe</mml:mi></mml:mrow><mml:mrow><mml:mn>0.953</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi>Co</mml:mi></mml:mrow><mml:mrow><mml:mn>0.047</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mo stretchy="false">)</mml:mo></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml

Zhang, Qiang; Fernandes, Rafael M.; Lamsal, Jagat; Yan, Jiaqiang; Chi, Songxue; Tucker, Gregory S.; Pratt, Dan E.; Lynn, J. W.; McCallum, R. W.; Canfield, Paul C.; Lograsso, Thomas A.; Goldman, A. I.; Vaknin, David; McQueeney, R. J.

doi:10.1103/physrevlett.114.057001

Cited by 34 publications

(41 citation statements)

References 77 publications

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“…The orbital fluctuation mechanism produces a sign preserving s ++ -wave pairing, where the order parameters of the electron and hole pockets do not change their relative signs 14,15 , while the spin fluctuation mechanism favors a sign-changing s-wave pairing, where the electron and the hole Fermi surfaces have order parameters with opposite signs 16,17 . Furthermore, in the spin-fluctuation-based pairing theory the possibile existence of order-parameter nodes is reported in both singlet and triplet superconducting states 18,19 .…”

Section: Introductionmentioning

confidence: 99%

Impurity scattering effects on the superconducting properties and the tetragonal-to-orthorhombic phase transition in FeSe

Abdel-Hafiez

Brisbois

et al. 2016

Phys. Rev. B

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A comprehensive study of the doping dependence phase diagram of FeSe-based superconductors is still required due to the lack of a clean and systematic means of doping control. Here, we report on the magneto-optical imaging, thermodynamic and transport properties, as well as in-situ angleresolved photoemission spectroscopy (ARPES) studies, on the impurity scattering in stoichiometric FeSe single crystals. Co doping at the Fe site, is found to decrease the superconducting transition temperature (Tc). The upper critical field and specific heat all indicate a possible multiband with strong coupling superconductivity in the Co-doped system. A remarkable feature in FeSe is that its temperature dependent resistivity exhibits a wide hump at high temperatures, signature of a crossover from a semiconducting-like behavior to metallic behavior. ARPES data between 180 K and 282 K indicates the existence of chemical potential shift with increasing thermal excitations, resulting in a change of the Fermi surface topology and exhibiting a semi-metal behavior. We found that the temperature induced-Lifshitz transition is much higher than the temperature for the nematic order. A structural tetragonal-to-orthorhombic phase transition (Ts) (consequence of the electronic nematicity) is suppressed by either physical or chemical pressures. Due to the reconstruction of the Fermi surface at Ts, specific heat anomalies at Ts present ∆Cp/Ts ≈ γn, the Sommerfield coefficient at low temperature. This reflects additional electronic instability in the FeSe1−xSx system.

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Section: Introductionmentioning

confidence: 99%

Impurity scattering effects on the superconducting properties and the tetragonal-to-orthorhombic phase transition in FeSe

Abdel-Hafiez

Brisbois

et al. 2016

Phys. Rev. B

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“…3(d)). This is likely associated with changes in the J a and J b nearest-neighbor exchange integrals, partially releasing the magnetic frustration and allowing for increased magnetic correlation lengths [32].…”

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confidence: 99%

“…Despite such extensive investigations in several materials, no Raman study of the nematic fluctuations in the key parent compound LFAO has been carried out yet. In this work, we fill this gap and investigate in detail the temperature dependence of both electronic and phonon Raman scattering in LFAO.Details of the synthesis procedure and basic characterization of the crystal employed in this work, showing T S = 155 K and T AF M = 140 K, are described elsewhere [12,32]. A fresh ab surface with ∼ 1 × 1 mm 2 was obtained by cleaving the crystal and immediately mounting it at the cold finger of a closed-cycle He cryostat.…”

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Nematic fluctuations and phase transitions in LaFeAsO: A Raman scattering study

et al. 2017

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Raman scattering experiments on LaFeAsO with splitted antiferromagnetic (TAF M = 140 K) and tetragonal-orthorhombic (TS = 155 K) transitions show a quasi-elastic peak (QEP) in B2g symmetry (2 Fe tetragonal cell) that fades away below ∼ TAF M and is ascribed to electronic nematic fluctuations. A scaling of the reported shear modulus with the T −dependence of the QEP height rather than the QEP area indicates that magnetic degrees of freedom drive the structural transition. The large separation between TS and TAF M in LaFeAsO compared with their coincidence in BaFe2As2 manifests itself in slower dynamics of nematic fluctuations in the former. The discovery of Fe-based superconductors (FeSCs) with high transition temperatures (above 100 K in FeSe films [1]) triggered much interest on these materials [2][3][4][5]. Nematicity, characterized by large in-plane electronic transport anisotropy [6], is normally observed below a tetragonal-orthorhombic transition temperature T S , and seems to be also present in other high-T c superconductors [7]. Also, divergent nematic susceptibility in the optimal doping regime suggests that nematic fluctuations play an important role in the superconducting pairing mechanism [8]. Thus, investigations of the nematic order and fluctuations in FeSCs and their parent materials are pivotal to unraveling the origin of high-T c superconductivity. Clearly, it is necessary to identify the primary order parameter associated with the nematic phase [4, 5]. A relation between nematicity and magnetism is suggested by the near coincidence between T S and the antiferromagnetic (AFM) ordering temperature T AF M in some materials, most notably BaFe 2 As 2 with T AF M ∼ T S = 138 K [9,10]. In fact, the magnetic ground state is a stripe AFM phase that breaks the 4-fold tetragonal symmetry of the lattice (see Fig. 1(a)), providing a natural mechanism for electronic anisotropy. On the other hand, T S and T AF M are significantly separated for LaFeAsO (LFAO) (T AF M = 140 K and T S = 155 K) [11][12][13], while FeSe does not order magnetically at ambient pressure but still shows a nematic transition at T S = 90 K [14], motivating suggestions that the nematic transition may be driven by charge/orbital degrees of freedom rather than magnetism in the latter [16,17]. However, even for FeSe the magnetic scenario may still apply [18]. In * Present address: Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.Ba(Fe 1−x Co x ) 2 As 2 and other doped systems, the splitting between T AF M and T S increases with doping [9,15]. Overall, the primary order parameter that drives the structural/nematic transition at T S and the dominating mechanism of T AF M /T S separation in parent FeSCs are not fully settled yet.Raman scattering was recently employed as a probe of nematic fluctuations in FeSCs and their parent materials. In A(Fe 1−x Co x ) 2 As 2 (A = Ca, Sr, Ba, Eu) [1, 4,19,21,22,24,25], Ba 1−p K p Fe 2 As 2 [25], FeSe [26,27] and NaFe 1−x Co x As [28], a quasi-elastic ...

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“…Indeed, neutron scattering experiments in both twinned 44 and detwinned 45 samples find enhanced magnetic fluctuations in the nematic phase. However, our data presented in Fig.…”

Section: 40mentioning

confidence: 99%

NMR study of nematic spin fluctuations in a detwinned single crystal of underdopedBa(Fe1−xCox)2As2
Kissikov
¹
,
Dioguardi
²
,
Timmons
³

et al. 2016
Phys. Rev. B
16
0
21
0
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Neutron-Scattering Measurements of Spin Excitations in LaFeAsO andBa(Fe0.953Co0.047)2

Cited by 34 publications

References 77 publications

Impurity scattering effects on the superconducting properties and the tetragonal-to-orthorhombic phase transition in FeSe

Impurity scattering effects on the superconducting properties and the tetragonal-to-orthorhombic phase transition in FeSe

Nematic fluctuations and phase transitions in LaFeAsO: A Raman scattering study

NMR study of nematic spin fluctuations in a detwinned single crystal of underdopedBa(Fe1−xCox)2As2
Kissikov
¹
,
Dioguardi
²
,
Timmons
³

et al. 2016
Phys. Rev. B
16
0
21
0
View full text Add to dashboard Cite

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Neutron-Scattering Measurements of Spin Excitations in LaFeAsO andBa(Fe0.953Co0.047)2

Cited by 34 publications

References 77 publications

Impurity scattering effects on the superconducting properties and the tetragonal-to-orthorhombic phase transition in FeSe

Impurity scattering effects on the superconducting properties and the tetragonal-to-orthorhombic phase transition in FeSe

Nematic fluctuations and phase transitions in LaFeAsO: A Raman scattering study

NMR study of nematic spin fluctuations in a detwinned single crystal of underdopedBa(Fe1−xCox)2As2Kissikov1, Dioguardi2, Timmons3 et al. 2016Phys. Rev. B160210View full textAdd to dashboardCite

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NMR study of nematic spin fluctuations in a detwinned single crystal of underdopedBa(Fe1−xCox)2As2
Kissikov
¹
,
Dioguardi
²
,
Timmons
³

et al. 2016
Phys. Rev. B
16
0
21
0
View full text Add to dashboard Cite