Related papers: Direct observation of a Fermi surface and supercon…
Here we apply high resolution angle-resolved photoemission spectroscopy (ARPES) using a wide excitation energy range to probe the electronic structure and the Fermi surface topology of the Ba1-xKxFe2As2 (Tc = 32 K) superconductor. We find…
Recent observations of two nodeless gaps in superconducting CeCu$_2$Si$_2$ have raised intensive debates on its exact gap symmetry, while a satisfactory theoretical basis is still lacking. Here we propose a phenomenological approach to…
We carried out high resolution angle-resolved photoemission measurements on the electronic structure and superconducting gap of K_0.68Fe_1.79Se_2 (T_c=32 K) and (Tl_0.45K_0.34)Fe_1.84Se_2 (T_c=28 K) superconductors. In addition to the…
Conventional superconductivity follows Bardeen-Cooper-Schrieffer(BCS) theory of electrons-pairing in momentum-space, while superfluidity is the Bose-Einstein condensation(BEC) of atoms paired in real-space. These properties of solid metals…
High resolution laser-based angle-resolved photoemission measurements were carried out on an overdoped $Bi_2Sr_2CaCu_2O_{8+\delta}$ superconductor with a Tc of 75 K. Two Fermi surface sheets caused by bilayer splitting are clearly…
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…
We report electronic structure calculations for BaTi$_2$Sb$_2$O and discuss the results in relation to the observed superconductivity of this material when hole doped with Na. The Fermi surface shows several sheets. These include a nested…
The phase variation of the superconducting gap over the (normal) Fermi surface of the high-temperature superconductors remains a significant unresolved question. Is the phase of the gap constant, does it change sign, or is it perhaps…
In conventional BCS superconductors, the quantum condensation of superconducting electron pairs is understood as a Fermi surface (FS) instability, in which the low-energy electrons are paired by attractive interactions. Whether this…
We have performed high-resolution angle-resolved photoemission spectroscopy on Fe-based superconductor LiFeAs (Tc = 18 K). We reveal multiple nodeless superconducting (SC) gaps with 2D/kBTc ratios varying from 2.8 to 6.4, depending on the…
We report the discovery of a self-doped multi-layer high Tc superconductor Ba2Ca3Cu4O8F2(F0234) which contains distinctly different superconducting gap magnitudes along its two Fermi surface(FS) sheets. While formal valence counting would…
Single crystal antiferromagnetic USb2 was studied at 15K by angle-resolved photoemission with an overall energy resolution of 24 meV. The measurements unambiguously show the dispersion of extremely narrow bands situated near the Fermi…
We present measurements of the superconducting gap of URu$_2$Si$_2$ made with scanning tunneling microscopy (STM) using a superconducting tip of Al. We find tunneling conductance curves with a finite value at the Fermi level. The density of…
We have performed high-resolution angle-resolved photoemission spectroscopy on the optimally-doped Ba$_{0.6}$K$_{0.4}$Fe$_2$As$_2$ compound and determined the accurate momentum dependence of the superconducting (SC) gap in four…
Using angle-resolved photoemission spectroscopy (ARPES), we have observed the band structure, Fermi surface and their doping dependences in La2-xSrxCuO4. The results reveal that the Fermi surface undergoes a dramatic change: it is hole-like…
We measured the Fermi surface of the recently discovered superconductor Ag5Pb2O6 via a de Haas-van Alphen rotation study. Two frequency branches were observed and identified with the neck and belly orbits of a very simple, nearly free…
Superconducting EuFe2(As0.82P0.18)2 single crystals are investigated by infrared spectroscopy in a wide frequency range. Below Tc=28K a superconducting gap forms at 2\Delta_{0} = 9.5 meV = 3.8 k_B T_c causing the reflectivity to sharply…
We present Angle-Resolved Photoemission Spectroscopy measurements of the quasi-one dimensional superconductor K$_2$Cr$_3$As$_3$. We find that the Fermi surface contains two Fermi surface sheets, with linearly dispersing bands not displaying…
Angle-resolved photoemission spectroscopy is the leading tool for studying the symmetry and structure of the order parameter in superconductors. The recent improvement of the technique made it possible to detect the superconducting energy…
Since the discovery of heavy-fermion superconductivity in CeCu$_{2}$Si$_{2}$, the material has attracted great interest particularly with regard to the nature of the superconducting pairing and its mechanism. Consequently, it is essential…