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We report very highly resolved photoemission spectra of NiS(1-x)Se(x) across the so-called metal-insulator transition as a function of temperature as well as composition. The present results convincingly demonstrate that the low…

Strongly Correlated Electrons · Physics 2009-10-31 D. D. Sarma , S. R. Krishnakumar , Nirmala Chandrasekharan , E. Weschke , C. Schüßler-Langeheine , L. Kilian , G. Kaindl

We report the first photoemission study of Fe1+xTe - the host compound of the newly discovered iron-chalcogenide superconductors. Our results reveal a pair of nearly electron- hole compensated Fermi pockets, strong Fermi velocity…

Superconductivity · Physics 2013-05-29 Y. Xia , D. Qian , L. Wray , D. Hsieh , G. F. Chen , J. L. Luo , N. L. Wang , M. Z. Hasan

We use neutron diffraction to study the temperature evolution of the average structure and local lattice distortions in insulating and superconducting potassium iron selenide K$_y$Fe$_{1.6+x}$Se$_2$. In the high temperature paramagnetic…

Superconductivity · Physics 2015-06-19 Scott V Carr , Despina Louca , Joan Siewenie , Q. Huang , Aifeng Wang , Xianhui Chen , Pengcheng Dai

The electronic structure of the enigmatic iron-based superconductor FeSe has puzzled researchers since spectroscopic probes failed to observe the expected electron pocket at the $Y$ point in the 1-Fe Brillouin zone. It has been speculated…

Superconductivity · Physics 2021-02-16 Daniel Steffensen , Andreas Kreisel , P. J. Hirschfeld , Brian M. Andersen

We present a calculation of a 'modulated' superconducting state in iron-selenide superconductors. The zero-momentum $d-$wave pairing breaks the translational symmetry of the conventional BaFe$_2$Se$_2$-like crystal of $I4/mmm$ space group.…

Superconductivity · Physics 2011-09-20 Tanmoy Das , A. V. Balatsky

We studied the electronic structure of the heavy fermion compound Yb(Ru$_{1-x}$Rh$_{x}$)$_2$Ge$_2$ with $x=0$ and nominally $x=0.125$ using ARPES and LDA calculations. We find a valence band structure of Yb corresponding to a non-integer…

Strongly Correlated Electrons · Physics 2019-03-04 H. Pfau , E. W. Rosenberg , P. Massat , B. Moritz , M. Hashimoto , D. Lu , I. R. Fisher , Z. -X. Shen

We investigate the effect of disordered vacancies on the normal-state electronic structure of the newly discovered alkali-intercalated iron selenide superconductors. To this end we use a recently developed Wannier function based method to…

Disordered Systems and Neural Networks · Physics 2012-10-10 Tom Berlijn , P. J. Hirschfeld , Wei Ku

Among numerous hypotheses, recently proposed to explain superconductivity in iron-based superconductors [1-9], many consider Fermi surface (FS) nesting [2, 4, 8, 10] and dimensionality [4, 9] as important contributors. Precise determination…

The isovalent-substituted iron-pnictide superconductor SrFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$ ($x$=0.35) has a slightly higher optimum critical temperature than the similar system BaFe$_{2}$(As$_{1-x}$P$_{x}$)$_{2}$, and its parent compound…

The magnetic and electronic phase diagram of a model for the quasi-one-dimensional alkali metal iron selenide compound Na$_2$FeSe$_2$ is presented. The novelty of this material is that the valence of iron is Fe$^{2+}$ contrary to most other…

Strongly Correlated Electrons · Physics 2020-07-29 Bradraj Pandey , Ling-Fang Lin , Rahul Soni , Nitin Kaushal , Jacek Herbrych , Gonzalo Alvarez , Elbio Dagotto

We have studied the electronic structure of EuFe2As2-xPx using high resolution angle-resolved photoemission spectroscopy. Upon substituting As with the isovalent P, which leads to a chemical pressure and to superconductivity, we observe a…

With single crystal X-ray diffraction studies, we compare the structures of three sample showing optimal superconductivity, K0.774(4)Fe1.613(2)Se2, K0.738(6)Fe1.631(3)Se2 and Cs0.748(2)Fe1.626(1)Se2. All have an almost identical ordered…

Superconductivity · Physics 2015-05-27 P. Zavalij , Wei Bao , X. F. Wang , J. J. Ying , X. H. Chen , D. M. Wang , J. B. He , X. Q. Wang , G. F Chen , P-Y Hsieh , Q. Huang , M. A. Green

We use angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT) calculations to study the electronic structure of CaFe$_2$As$_2$ in previously unexplored collapsed tetragonal (CT) phase. This unusual phase of…

One of the ultimate goals of the study of iron-based superconductors is to identify the common feature that produces the high critical temperature (Tc). In the early days, based on a weak-coupling viewpoint, the nesting between hole- and…

Layered indium selenides ($In_{2}Se_{3}$) have recently been discovered to host robust out-of-plane and in-plane ferroelectricity in the $\alpha$ and $\beta$' phases, respectively. In this work, we utilise angle-resolved photoelectron…

The 122$^{*}$ series of iron-chalcogenide superconductors, for example K$_x$Fe$_{2-y}$Se$_{2}$, only possesses electron Fermi pockets. Their distinctive electronic structure challenges the picture built upon iron pnictide superconductors,…

We present LDA band structure of novel hole doped high temperature superconductors (Tc~30K) KxFe2Se2 and CsxFe2Se2 and compare it with previously studied electronic structure of isostructural FeAs superconductor BaFe2As2 (Ba122). We show…

Superconductivity · Physics 2011-04-20 I. A. Nekrasov , M. V. Sadovskii

We use scanning tunneling spectroscopy to investigate the filled and empty electronic states of superconducting single-unit-cell FeSe deposited on SrTiO$_3$(001). We map the momentum-space band structure by combining quasiparticle…

We performed a high-resolution angle-resolved photoemission spectroscopy study of the Tl$_{0.63}$K$_{0.37}$Fe$_{1.78}$Se$_2$ superconductor ($T_c=29$ K). We show the existence of two electronlike bands at the M$(\pi, 0)$ point which cross…

Superconductivity · Physics 2011-02-23 X. -P. Wang , T. Qian , P. Richard , P. Zhang , J. Dong , H. -D. Wang , C. -H. Dong , M. -H. Fang , H. Ding

The structural and electronic properties of hypothetical Ru$_x$Fe$_{1-x}$Se and Ru$_x$Fe$_{1-x}$Te systems have been investigated from first principles within the density functional theory (DFT). Reasonable values of lattice parameters and…

Superconductivity · Physics 2014-12-15 M. J. Winiarski , M. Samsel-Czekała , A. Ciechan