Collapsed Tetragonal Phase Transition of Ca(Fe1-xRhx)2As2Studied by Photoemission Spectroscopy

Tsubota, Koji; Wakita, Takanori; Nagao, Hiroki; Hiramatsu, Chiaki; Ishiga, Toshihiko; Sunagawa, Masanori; Ono, Kanta; Kumigashira, Hiroshi; Danura, Masataka; Kudo, Kazuhiro; Nohara, M.; Muraoka, Yuji; Yokoya, Takayoshi

doi:10.7566/jpsj.82.073705

Cited by 14 publications

(21 citation statements)

References 28 publications

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“…In the collapsed phase, a new doublet appears at high binding energies, showed in red, probably as a result of a highest electronic density around As in this structure. We observed a similar shift to high energy in collapsed CaFe 2 As 2 (not shown), as also reported in [18]. This evidences that the last two compounds have collapsed structures.…”

Section: Experimental and Calculation Detailssupporting

confidence: 90%

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: Experimental and Calculation Detailssupporting

confidence: 90%

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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“…Similar with (Ca 0.34 Na 0.66 )Fe 2 As 2 in cT phase, both the absence of superconductivity and the recovery of FL behaviors have also been observed in cT phase of CaFe 2 As 2 or doped Ca122 Fe pnictides. 39,[44][45][46][47] In summary, we have shown that the T c of (Ca 0.34 Na 0.66 )Fe 2 As 2 decreases nearly linearly with a slope dT c /dP ∼ −1.7 K/GPa with increasing pressure. Anomalous non-FL behaviors of R-T curves are also observed at lower pressures in (Ca 0.34 Na 0.66 )Fe 2 As 2 , whereas the recovery of FL transport properties corresponds to the disappearance of superconductivity.…”

Section: Resultsmentioning

confidence: 99%

Pressure-induced shift of Tc and structural transition in “122” type pnictide superconductor Ca0.34Na0.66Fe2As2

Zhang

Zhao

et al. 2016

AIP Advances

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The effect of pressure on superconductivity of “122” type Ca1-xNaxFe2As2 (x=0.66) single crystal is investigated through the temperature dependence of resistance measurement. Optimal Na doped (Ca0.34Na0.66)Fe2As2 shows a superconducting transition with Tc ∼ 33 K at ambient pressure. With application of pressure, Tc decreases nearly linearly with dTc/dP ∼ − 1.7K/GPa at pressures lower than 2 GPa, and disappears gradually at higher pressure. The disappearance of superconductivity is also companied with the recovery of standard Fermi liquid behaviors of the normal-state transport properties. Moreover, (Ca0.34Na0.66)Fe2As2 exhibits a tetragonal (T) to collapsed-tetragonal (cT) transition at about 3 GPa. The evolution of non-Fermi liquid behaviors and superconductivity under pressure are both related to the interband fluctuations.

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“…In our samples, the transition is done by lowering temperature and the c axis is reduced by about 5%-6%. This modification of the crystal structure is at the origin of a reorganization of the Fermi surface and electronic structure of the compound [8,9,[12][13][14], which has been studied within DFT [8,13,15,16] and very recently within combined density functional dynamical mean field theory ("DFT+DMFT") [17,18]. The electronic structure of CaFe 2 As 2 and of its different phases has also been probed by photoemission experiments [13,19,20].…”

Section: Introductionmentioning

confidence: 99%

Tetragonal and collapsed-tetragonal phases ofCaFe2As2: A view from angle-resolved photoemission and dynamical mean-field theory

et al. 2016

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We present a study of the tetragonal to collapsed-tetragonal transition of CaFe2As2 using angleresolved photoemission spectroscopy and dynamical mean field theory-based electronic structure calculations. We observe that the collapsed-tetragonal phase exhibits reduced correlations and a higher coherence temperature due to the stronger Fe-As hybridization. Furthermore, a comparison of measured photoemission spectra and theoretical spectral functions shows that momentumdependent corrections to the density functional band structure are essential for the description of low-energy quasiparticle dispersions. We introduce those using the recently proposed combined "Screened Exchange + Dynamical Mean Field Theory" scheme.

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Collapsed Tetragonal Phase Transition of Ca(Fe_1-xRh_x)₂As₂Studied by Photoemission Spectroscopy

Cited by 14 publications

References 28 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-induced shift of Tc and structural transition in “122” type pnictide superconductor Ca0.34Na0.66Fe2As2

Tetragonal and collapsed-tetragonal phases ofCaFe2As2: A view from angle-resolved photoemission and dynamical mean-field theory

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