Structural Origin of the Anomalous Temperature Dependence of the Local Magnetic Moments in the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>CaFe</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mrow><mml:mi>As</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>Family of Materials

Ortenzi, Luciano; Gretarsson, H.; Kasahara, S.; Matsuda, Yuji; Shibauchi, T.; Finkelstein, K. D.; Wu, Weixing; Julian, S. R.; Kim, Yong Baek; Mazin, I. I.; Boeri, Lilia

doi:10.1103/physrevlett.114.047001

Cited by 33 publications

(37 citation statements)

References 46 publications

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“…In CaFe 2 As 2 , a change of correlations is expected at the collapsed transition [39,40], because of the disappearance of local magnetic moments [41][42][43]. This is partially supported by ARPES data [44][45][46].…”

Section: Discussionmentioning

confidence: 79%

Influence of surface symmetry breaking on the magnetism, collapsing, and three-dimensional dispersion of the Co pnictidesACo2As2(A=Ba, Sr

et al. 2016

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We use angle-resolved photoemission (ARPES) to study the three dimensional (3D) electronic structure of Co pnictides ACo2As2 with A=Ba, Sr, Ca or a mixture of Sr and Ca. These compounds are isostructural to Fe based superconductors, but have one more electron in the Co 3d orbitals. Going from Ba to Ca, they become more and more 3D, eventually forming a "collapsed" tetragonal phase, where the distance between CoAs layers is markedly reduced. We observe with ARPES the periodicity of the electronic structure as a function of kz (i.e. perpendicularly to CoAs layers) and find that it matches in each case that expected from the distance between the planes in the bulk. However, the electronic structure is better fitted by a calculation corresponding to a slab with 2 CoAs layers than to the bulk structure. We attribute this to subtle modifications of the 2D electronic structure induced by the truncation of the 3D dispersion at the surface in the ARPES measurement. We further study how this affects the electronic properties. We show that, despite this distortion, the electronic structure of CaCo2As2 is essentially that expected for a collapsed phase. Electronic correlations produce a renormalization of the electronic structure by a factor 1.4, which is not affected by the transition to the collapsed state. On the other hand, a small shift of the Fermi level reduces the density of states in the eg bands and suppresses the magnetic transition expected in CaCo2As2. Our study evidences that observing the 3D bulk periodicity is not sufficient to ensure bulk sensitivity. It further gives direct information on the role of 3D interactions, mostly governed by Co-As hybridization, among eg and t2g orbitals. It is also useful to better understand the electronic structure of Fe superconductors and the range of validity of ARPES measurements.

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Section: Discussionmentioning

confidence: 79%

Influence of surface symmetry breaking on the magnetism, collapsing, and three-dimensional dispersion of the Co pnictidesACo2As2(A=Ba, Sr

et al. 2016

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“…Thus, in some studies, a negative U correction was adopted to better describe the 122-type Fe-based materials [47,48]. Alternatively, the exchange and correlation kernels were rescaled by an appropriate factor [49]. In the present study, both GGA+U and pure GGA have been tested, and we found that the later provides a better description of AFe 2 X 3 (regarding its crystalline constants, magnetic moments, as well as band gaps).…”

Section: Methodsmentioning

confidence: 75%

Pressure-driven phase transition from antiferromagnetic semiconductor to nonmagnetic metal in the two-leg ladders AFe2X3 ( A=Ba,K

et al. 2017

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The recent discovery of superconductivity in BaFe2S3 [Takahashi et al., Nat. Mater. 14, 1008(2015] has stimulated considerable interest in 123-type iron chalcogenides. This material is the first reported iron-based two-leg ladder superconductor, as opposed to the prevailing two-dimensional layered structures of the iron superconductors family. Once the hydrostatic pressure exceeds 11 GPa, BaFe2S3 changes from a semiconductor to a superconductor below 24 K. Although previous calculations correctly explained its ground state magnetic state and electronic structure, the pressure induced phase transition was not successfully reproduced. In this work, our first principles calculations find that with increasing pressure the lattice constants as well as local magnetic moments are gradually suppressed, followed by a first-order magnetic transition at a critical pressure, with local magnetic moments dropping to zero suddenly. Our calculations suggests that the self-doping caused by electrons transferred from S to Fe may play a key role in this transition. The development of a nonmagnetic metallic phase at high pressure may pave the way to superconductivity. As extensions of this effort, two other 123-type iron chalcogenides, KFe2S3 and KFe2Se3, have also been investigated. KFe2S3 also displays a first-order transition with increasing pressure, but KFe2Se3 shows instead a second-order, or weakly first-order, transition. The required pressures for KFe2S3 and KFe2Se3 to quench the magnetism are higher than for BaFe2S3. Further experiments can confirm the predicted first-order nature of the transition in BaFe2S3 and KFe2S3, as well as the possible metallic/superconductivity state in other 123-type iron chalcogenides under high pressure.

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“…If we associate the approach to the cT phase with an increase in the interlayer As-As hybridization [26,[58][59][60][61][62], then it is possible that the Fe magnetic moment is concomitantly decreasing. Such an effect is shown to be the case for CaFe 2 (As 1−x P x ) 2 , x = 0.033 and 0.055, and Ca 0.78 La 0.22 Fe 2 As 2 [63,64]. Thus we suggest that the suppression of χ (Q stripe ,E) with decreasing temperature for Ca(Fe 0.97 Co 0.03 ) 2 As 2 may be due to a decrease in Fe moment tied to the decrease in c. No such suppression in χ (Q stripe ,E) is observed for x = 0.026 between T = 90 and 20 K, because c increases only weakly upon cooling through T S,N , as shown in Fig.…”

Section: Discussionmentioning

confidence: 82%

Doping evolution of spin fluctuations and their peculiar suppression at low temperatures in Ca(Fe1−xCox)2As2
Sapkota¹,
Das²,
Böhmer³
et al. 2018
Phys. Rev. B
7
2
12
0
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Results of inelastic neutron scattering measurements are reported for two annealed compositions of Ca(Fe1-xCox)(2)As-2, x = 0.026 and 0.030, which possess stripe-type antiferromagnetically ordered and superconducting ground states, respectively. In the AFM ground state, well-defined and gapped spin waves are observed for x = 0.026, similar to the parent CaFe2As2 compound. We conclude that the well-defined spin waves are likely to be present for all x corresponding to the AFM state. This behavior is in contrast to the smooth evolution to overdamped spin dynamics observed in Ba(Fe1-xCox)(2)As-2, wherein the crossover corresponds to microscopically coexisting AFM order and SC at low temperature. The smooth evolution is likely absent in Ca(Fe1-xCox)(2)As-2 due to the mutual exclusion of AFM ordered and SC states. Overdamped spin dynamics characterize paramagnetism of the x = 0.030 sample and high-temperature x = 0.026 sample. A sizable loss of magnetic intensity is observed over a wide energy range upon cooling the x = 0.030 sample, at temperatures just above and within the superconducting phase. This phenomenon is unique amongst the iron-based superconductors and is consistent with a temperature-dependent reduction in the fluctuating moment. One possible scenario ascribes this loss of moment to a sensitivity to the c-axis lattice parameter in proximity to the nonmagnetic collapsed tetragonal phase and another scenario ascribes the loss to a formation of a pseudogap. Results of inelastic neutron scattering measurements are reported for two annealed compositions of Ca(Fe 1−x Co x ) 2 As 2 , x = 0.026 and 0.030, which possess stripe-type antiferromagnetically ordered and superconducting ground states, respectively. In the AFM ground state, well-defined and gapped spin waves are observed for x = 0.026, similar to the parent CaFe 2 As 2 compound. We conclude that the well-defined spin waves are likely to be present for all x corresponding to the AFM state. This behavior is in contrast to the smooth evolution to overdamped spin dynamics observed in Ba(Fe 1−x Co x ) 2 As 2 , wherein the crossover corresponds to microscopically coexisting AFM order and SC at low temperature. The smooth evolution is likely absent in Ca(Fe 1−x Co x ) 2 As 2 due to the mutual exclusion of AFM ordered and SC states. Overdamped spin dynamics characterize paramagnetism of the x = 0.030 sample and high-temperature x = 0.026 sample. A sizable loss of magnetic intensity is observed over a wide energy range upon cooling the x = 0.030 sample, at temperatures just above and within the superconducting phase. This phenomenon is unique amongst the iron-based superconductors and is consistent with a temperature-dependent reduction in the fluctuating moment. One possible scenario ascribes this loss of moment to a sensitivity to the c-axis lattice parameter in proximity to the nonmagnetic collapsed tetragonal phase and another scenario ascribes the loss to a formation of a pseudogap. Disciplines Condensed Matter Physics | Physics

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Structural Origin of the Anomalous Temperature Dependence of the Local Magnetic Moments in theCaFe2As2Family of Materials

Cited by 33 publications

References 46 publications

Influence of surface symmetry breaking on the magnetism, collapsing, and three-dimensional dispersion of the Co pnictidesACo2As2(A=Ba, Sr

Influence of surface symmetry breaking on the magnetism, collapsing, and three-dimensional dispersion of the Co pnictidesACo2As2(A=Ba, Sr

Pressure-driven phase transition from antiferromagnetic semiconductor to nonmagnetic metal in the two-leg ladders AFe2X3 ( A=Ba,K

Doping evolution of spin fluctuations and their peculiar suppression at low temperatures in Ca(Fe1−xCox)2As2
Sapkota¹,
Das²,
Böhmer³
et al. 2018
Phys. Rev. B
7
2
12
0
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Structural Origin of the Anomalous Temperature Dependence of the Local Magnetic Moments in theCaFe2As2Family of Materials

Cited by 33 publications

References 46 publications

Influence of surface symmetry breaking on the magnetism, collapsing, and three-dimensional dispersion of the Co pnictidesACo2As2(A=Ba, Sr

Influence of surface symmetry breaking on the magnetism, collapsing, and three-dimensional dispersion of the Co pnictidesACo2As2(A=Ba, Sr

Pressure-driven phase transition from antiferromagnetic semiconductor to nonmagnetic metal in the two-leg ladders AFe2X3 ( A=Ba,K

Doping evolution of spin fluctuations and their peculiar suppression at low temperatures in Ca(Fe1−xCox)2As2Sapkota1, Das2, Böhmer3 et al. 2018Phys. Rev. B72120View full textAdd to dashboardCite

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Doping evolution of spin fluctuations and their peculiar suppression at low temperatures in Ca(Fe1−xCox)2As2
Sapkota¹,
Das²,
Böhmer³
et al. 2018
Phys. Rev. B
7
2
12
0
View full text Add to dashboard Cite