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The role of electronic Coulomb correlations in iron-based superconductors is an important open question. We provide theoretical evidence for strong correlation effects in the FeSe compound, based on dynamical mean field calculations. A…

Strongly Correlated Electrons · Physics 2010-09-23 Markus Aichhorn , Silke Biermann , Takashi Miyake , Antoine Georges , Masatoshi Imada

By using solid state reaction method, we have synthesized the Pd-doped superconductor SrFe2-xPdxAs2. The systematic evolution of the lattice constants indicated that the Fe ions were successfully replaced by the Pd. By increasing the doping…

Superconductivity · Physics 2016-06-28 Xiyu Zhu , Fei Han Peng Cheng , Bing Shen , Hai-Hu Wen

Using femtosecond time- and angle-resolved photoemission spectroscopy we investigate the effect of electron doping on the electron dynamics in Ba(Fe_{1-x}Co_x)_2As_2 in a range of 0 < x < 0.15 at temperatures slightly above the N\'eel…

Superconductivity · Physics 2016-10-12 I. Avigo , S. Thirupathaiah , M. Ligges , T. Wolf , J. Fink , U. Bovensiepen

By substituting Fe with the 5d-transition metal Pt in BaFe2As2, we have successfully synthesized the superconductors BaFe2-xPtxAs2. The systematic evolution of the lattice constants indicates that the Fe ions were successfully replaced by…

Superconductivity · Physics 2015-05-18 Xiyu Zhu , Fei Han , Gang Mu , Jun Tang , Jing Ju , Katsumi Tanigaki , Hai-Hu Wen

The spin dynamics in single crystal, electron-doped Ba(Fe1-xCox)2As2 has been investigated by inelastic neutron scattering over the full range from undoped to the overdoped regime. We observe damped magnetic fluctuations in the normal state…

Superconductivity · Physics 2010-08-24 K. Matan , S. Ibuka , R. Morinaga , Songxue Chi , J. W. Lynn , A. D. Christianson , M. D. Lumsden , T. J. Sato

We present specific heat measurements on a series of BaFe2(As1-xPx)2 single crystals with phosphorous doping ranging from x = 0.3 to 0.55. Our results reveal that BaFe2(As1-xPx)2 follows the scaling Delta_C/Tc ~ Tc^2 remarkably well. The…

Superconductivity · Physics 2011-10-17 C. Chaparro , L. Fang , H. Claus , A. Rydh , G. W. Crabtree , V. Stanev , W. K. Kwok , U. Welp

While the superconducting transition temperature of hole-doped Ba_{1-x}K_{x}Fe_{2}As_{2} decreases past optimal doping, superconductivity does not completely disappear even for the fully doped KFe_{2}As_{2} compound. In fact,…

The recently discovered Fe-based superconductor (FeBS) LaFe2As2 seems to break away from an established pattern that doping FeBS beyond 0.2e/Fe destroys superconductivity. LaFe2As2 has an apparent doping of 0.5e, yet superconducts at 12.1…

Superconductivity · Physics 2020-01-03 I. I. Mazin , Makoto Shimizu , Nayuta Takemori , Harald O. Jeschke

We performed systematic thermal conductivity measurements on heavily hole-doped Ba$_{1-x}$K$_x$Fe$_2$As$_2$ single crystals with 0.747 $\leq x \leq$ 0.974. At $x$ = 0.747, the $\kappa_0/T$ is negligible, indicating nodeless superconducting…

Superconductivity · Physics 2016-01-20 X. C. Hong , A. F. Wang , Z. Zhang , J. Pan , L. P. He , X. G. Luo , X. H. Chen , S. Y. Li

We investigate the importance of superconducting order parameter fluctuations in the 122 family of Fe-based superconductors, using high-resolution specific heat and thermal expansion data of various Ba$_{1-x}$K$_x$Fe$_2$As$_2$ single…

We have studied EuFe$_{2}$(As$_{0.7}$P$_{0.3}$)$_{2}$ by the measurements of x-ray diffraction, electrical resistivity, thermopower, magnetic susceptibility, magnetoresistance and specific heat. Partial substitution of As with P results in…

Superconductivity · Physics 2009-04-02 Zhi Ren , Qian Tao , Shuai Jiang , Chunmu Feng , Cao Wang , Jianhui Dai , Guanghan Cao , Zhu'an Xu

We report a systematic and ab-initio electronic structure calculation of Ca0.75 M0.25 Fe2 As2 with M = Ca, Sr, Eu, La, Ce, Pr, Nd, Pm, Sm, Na, K, Rb. The recently reported experimentally observed structural trends in rare earths-doped CaFe2…

Superconductivity · Physics 2014-06-26 A. Sanna , G. Profeta , S. Massidda , E. K. U. Gross

We present a systematic investigation of the effect of H, B, C, and N interstitials on the electronic, lattice and magnetic properties of La(Fe,Si)$_{13}$ using density functional theory. The parent LaSiFe$_{12}$ alloy has a shallow,…

Materials Science · Physics 2017-12-14 Z. Gercsi , N. Fuller , K. G. Sandeman , A. Fujita

Using the merger of local density approximation and dynamical mean field theory, we show how electronic correlations increase the thermopower of Na$_{0.7}$CoO$_2$ by 200%. The newly revealed mechanism is an asymmetric shift of (quasi)…

Strongly Correlated Electrons · Physics 2015-03-19 P. Wissgott , A. Toschi , H. Usui , K. Kuroki , K. Held

We report a low-temperature specific heat study of high-quality single crystals of the heavily hole doped superconductor Ca$_{0.32}$Na$_{0.68}$Fe$_2$As$_2$. This compound exhibits bulk superconductivity with a transition temperature $T_c…

Electronic structure calculations indicate that the Sr2FeSbO6 double perovskite has a flat-band set just above the Fermi level that includes contributions from ordinary sub-bands with weak kinetic electron hopping plus a flat sub-band that…

Polycrystalline samples of underdoped (Ba1-xKx)Fe2As2 (x<=0.4) were synthesized and studied by x-ray powder diffraction, magnetic susceptibility, specific heat and 57Fe-Moessbauer-spectroscopy. The structural phase transition from…

We use cluster Dynamical Mean Field Theory to study the simplest models of correlated electrons, the Hubbard model and the t-J model. We use a plaquette embedded in a medium as a reference frame to compute and interpret the physical…

Strongly Correlated Electrons · Physics 2009-11-13 Kristjan Haule , Gabriel Kotliar

We report a systematic investigation of Ba[Fe(1-x)Co(x)]2As2 based on transport and 75-As NMR measurements, and establish the electronic phase diagram. We demonstrate that doping progressively suppresses the uniform spin susceptibility and…

Superconductivity · Physics 2009-01-14 F. L. Ning , K. Ahilan , T. Imai , A. S. Sefat , R. Jin , M. A. McGuire , B. C. Sales , D. Mandrus

The iron-based LaFeAsO$_{1-x}$F$_x$ recently discovered by Hosono's group is a fresh theoretical challenge as a new class of high-temperature superconductors. Here we describe the electronic structure of the material and the mechanism of…

Superconductivity · Physics 2009-11-13 Hideo Aoki