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Experiments on the iron-pnictide superconductors appear to show some materials where the ground state is fully gapped, and others where low-energy excitations dominate, possibly indicative of gap nodes. Within the framework of a 5-orbital…

Superconductivity · Physics 2015-03-13 A. F. Kemper , T. A. Maier , S. Graser , H. -P. Cheng , P. J. Hirschfeld , D. J. Scalapino

The electronic structures of FeAs-compounds strongly depend on the Fe-As bonding, which can not be described successfully by the local density approximation (LDA). Treating the multi-orbital fluctuations from $ab$-$initio$ by LDA+Gutzwiller…

Superconductivity · Physics 2010-01-26 G. T. Wang , Y. M. Qian , G. Xu , X. Dai , Z. Fang

This work investigates nematic fluctuations and electronic correlations in the hole-doped iron pnictide superconductor Ba$_{1-x}$K$_x$Fe$_2$As$_2$ by means of longitudinal and transverse elastoresistance measurements over a wide doping…

High-resolution angle-resolved photoelectron spectroscopy is used to examine the electronic band structure of FeTe$_{0.5}$Se$_{0.5}$ near the Brillouin zone center. A consistent separation of the $\alpha_{1}$ and $\alpha_{2}$ bands is…

Strongly Correlated Electrons · Physics 2016-06-14 P. D. Johnson , H. -B. Yang , J. D. Rameau , G. D. Gu , Z. -H. Pan , T. Valla , M. Weinert , A. V. Fedorov

We investigate the electronic state and structure transition of BaNi2As2, which shows a similar superconducting phase diagram as Fe-based superconductors. We construct the ten-orbital tight-binding model for BaNi2As2 by using the maximally…

Superconductivity · Physics 2013-08-05 Youichi Yamakawa , Seiichiro Onari , Hiroshi Kontani

The random-phase approximation (RPA) is here applied to a two-orbital model for the BiS2-based superconductors that was recently proposed by Usui et al., arXiv:1207.3888. Varying the density of doped electrons per Bi site, n, in the range…

Strongly Correlated Electrons · Physics 2013-03-05 George Martins , Adriana Moreo , Elbio Dagotto

Motivated by the experimental observation that superconductivity in bulk doped SrTiO$_{3}$ is enhanced as a putative ferroelectric quantum critical point (FE-QCP) is approached, we study the pairing instability of a cubic system in which…

Superconductivity · Physics 2020-05-06 Maria N. Gastiasoro , Thaís V. Trevisan , Rafael M. Fernandes

Half-metallicity in materials has been a subject of extensive research due to its potential for applications in spintronics. Ferromagnetic manganites have been seen as a good candidate, and aside from a small minority-spin pocket observed…

Strongly Correlated Electrons · Physics 2014-12-22 M. Baublitz , C. Lane , Hsin Lin , Hasnain Hafiz , R. S. Markiewicz , B. Barbiellini , Z. Sun , D. S. Dessau , A. Bansil

We present a systematic derivation of a minimal five-band tight-binding model for the description of the electronic structure of the recently discovered quasi one-dimensional superconductor K2Cr3As3. Taking as a reference the…

A neutron scattering study of heavily hole-overdoped superconducting KFe$_2$As$_2$ revealed a well-defined low-energy incommensurate spin fluctuation at [$\pi(1\pm2\delta$),0] with $\delta$ = 0.16. The incommensurate structure differs from…

Superconductivity · Physics 2011-02-15 C. H. Lee , K. Kihou , H. Kawano-Furukawa , T. Saito , A. Iyo , H. Eisaki , H. Fukazawa , Y. Kohori , K. Suzuki , H. Usui , K. Kuroki , K. Yamada

We report the signatures of dynamic spin fluctuations in the layered honeycomb Li$_3$Cu$_2$SbO$_6$ compound, with a 3$d$ S = 1/2 $d^9$ Cu$^{2+}$ configuration, through muon spin rotation and relaxation ($\mu$SR) and neutron scattering…

We have performed an angle-resolved photoemission spectroscopy (ARPES) study of the undoped and electron-doped iron pnictides BaFe2\_{-x}CoxAs2 (Ba122) (x=0, 0.14) and studied the Fermi surfaces (FSs) and band dispersions near the Fermi…

Electronic correlations in the Fe-pnictide BaFe2As2 are explored within LDA+DMFT, the combination of density functional theory with dynamical mean-field theory. While the correlated band structure is substantially renormalized there is only…

We investigate the in-plane anisotropy of Fe 3d orbitals occurring in a wide temperature and composition range of BaFe2(As1-xPx)2 system. By employing the angle-resolved photoemission spectroscopy, the lifting of degeneracy in dxz and dyz…

Superconductivity · Physics 2015-12-09 T. Sonobe , T. Shimojima , A. Nakamura , M. Nakajima , S. Uchida , K. Kihou , C. H. Lee , A. Iyo , H. Eisaki , K. Ohgushi , K. Ishizaka

We study the pairing mechanism in iron pnictide superconductors based on the five-orbital Hubbard-Holstein model. Due to Fe-ion oscillations, the s-wave superconducting (SC) state without sign reversal (s_{++}-wave state) is induced by…

Superconductivity · Physics 2010-10-18 Tetsuro Saito , Seiichiro Onari , Hiroshi Kontani

The superconducting fluctuations well inside the normal state of Fe-based superconductors were studied through measurements of the in-plane paraconductivity and magnetoconductivity in high quality BaFe(2-x)NixAs2 crystals with doping levels…

Superconductivity · Physics 2013-03-27 R. I. Rey , C. Carballeira , J. Mosqueira , S. Salem-Sugui , A. D. Alvarenga , H-Q. Luo , X-Y. Lu , Y-C. Chen , F. Vidal

Nematic phase transitions in high-temperature superconductors have a strong impact on the electronic properties of these systems. BaFe$_2$As$_2$,\@ with an established nematic transition around 137 K induced by magnetic fluctuations, and…

Superconductivity · Physics 2021-12-01 Michael Merz , Liran Wang , Thomas Wolf , Peter Nagel , Christoph Meingast , Stefan Schuppler

The absence of nesting between electron and hole-pockets in LiFeAs with $T_c = 18$K attracts great attention, as an important hint to understand the pairing mechanism of Fe-based superconductors. Here, we study the five-orbital model of…

We present a theoretical study of the dynamical spin susceptibility for the intriguing Fe-based superconductor FeSe, based on a tight-binding model developed to account for the temperature-dependent band structure in this system. The model…

Superconductivity · Physics 2016-01-05 A. Kreisel , Shantanu Mukherjee , P. J. Hirschfeld , Brian M. Andersen

We present a systematic analysis on the basis of ab initio calculations and many-body perturbation theory for clarifying the dominant fluctuation in complex charge-spin-orbital coupled systems. For a tight-binding multiband model obtained…

Strongly Correlated Electrons · Physics 2015-06-23 Amane Uehara , Hiroshi Shinaoka , Yukitoshi Motome