Robert Eder

Calorimetric evidence of multiband superconductivity in Ba ( Fe 0.925 Co 0.075 ) 2 As 2 single crystals

We report on the determination of the electronic heat capacity of a slightly overdoped (x = 0.075) Ba(Fe1-xCox)2As2 single crystal with a Tc of 21.4 K. Our analysis of the temperature dependence of the superconducting-state specific heat provides strong evidence for a two-band s-wave order parameter with gap amplitudes 2D1(0)/kBTc=1.9 and 2D2(0)/kBTc=4.4. Our result is consistent with the recently predicted s+- order parameter [I. I. Mazin et al., Phys. Rev. Lett. 101, 057003 (2008)].

Doping evolution of superconducting gaps and electronic densities of states in Ba(Fe1−xCox)2As2 iron pnictides

An extensive calorimetric study of the normal- and superconducting-state properties of Ba(Fe1−xCox)2As2 is presented for 0 0.06), which illustrates the strong competition between magnetism and superconductivity to monopolize the Fermi surface in the underdoped region and the filling of the hole bands for overdoped Ba(Fe1−xCox)2As2. All superconducting samples exhibit a residual electronic density of states of unknown origin in the zero-temperature limit, which is minimal at optimal doping but increases to the normal-state value in the strongly under- and over-doped regions. The remaining specific heat in the superconducting state is well described using a two-band model with isotropic s-wave superconducting gaps.

Doping-dependent quasiparticle band structure in cuprate superconductors

We present an exact diagonalization study of the single-particle spectral function in the so-called t-t{sup {prime}}-t{sup {prime}{prime}}-J model in two dimensions. As a key result, we find that hole doping leads to a major reconstruction of the quasiparticle band structure near ({pi},0): whereas for the undoped system the quasiparticle states near ({pi},0) are deep below the top of the band near ({pi}/2,{pi}/2), hole doping shifts these states up to E{sub F}, resulting in extended flat band regions close to E{sub F} and around ({pi},0). {copyright} {ital 1997} {ital The American Physical Society}

Multiband Superconductivity in KFe2As2 : Evidence for one Isotropic and several Liliputian Energy Gaps

We report a detailed low-temperature thermodynamic investigation (heat capacity and magnetization) of the superconducting state of KFe 2 As 2 for H || c axis. Our measurements reveal that the properties of KFe 2 As 2 are dominated by a relatively large nodeless energy gap (∆ 0 = 1.9 k B T c) which excludes d x 2 −y 2 symmetry. We prove the existence of several additional extremely small gaps (∆ 0 < 1.0 k B T c) that have a profound impact on the low-temperature and low-field behavior, similar to MgB 2 , CeCoIn 5 and PrOs 4 Sb 12. The zero-field heat capacity is analyzed in a realistic self-consistent 4-band BCS model which qualitatively reproduces the recent laser ARPES results of Okazaki et al. (Science 337 (2012) 1314). Our results show that extremely low-temperature measurements, i.e. T < 0.1 K,will be required in order to resolve the question of the existence of line nodes in this compound.

Evolution of the stripe phase as a function of doping from a theoretical analysis of angle-resolved photoemission data

By comparing single-particle spectral functions of

Strain-Driven Approach to Quantum Criticality in AFe2As2 with A=K, Rb, and Cs

t\ensuremath{-}J

Indications of spin-charge separation in the two-dimensional extended t - J model

and Hubbard models with recent angle-resolved photoemission results for

Single-particle excitations of the Kondo lattice

{\mathrm{La}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}{\mathrm{CuO}}_{4}

Of Substitution and Doping: Spatial and Electronic Structure in Fe Pnictides

(LSCO) and Nd-LSCO, we can decide where holes go as a function of doping, and more specifically, which type of stripe (bond-, site-centered) is present in these materials at a given doping. For dopings greater than about

Where do holes go in doped antiferromagnets and what is their relationship to superconductivity

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