Related papers: Structural quantum criticality and superconductivi…
BaFe2As2 is the parent compound of the '122' iron arsenide superconductors and crystallizes with the tetragonal ThCr2Si2 type structure, space group I4/mmm. A spin density wave transition at 140 K is accompanied by a symmetry reduction to…
We studied the effect of hydrostatic pressure (P) on the structural phase transitions and superconductivity in the ternary and pseudo-ternary iron arsenides CaFe2As2, BaFe2As2, and (Ba0.55K0.45)Fe2As2, by means of measurements of electrical…
We analyse several thermodynamic properties of the two-dimensional Kondo necklace using finite-temperature stochastic series expansion. In agreement with previous zero-temperature findings the model is shown to exhibit a quantum critical…
We investigate the role of ligand states in the electronic properties of CaFe2As2 using high-resolution hard x-ray photoemission spectroscopy (HAXPES) at different sample temperatures. Experimental results indicate that the binding energy…
Recently, superconductivity has been observed in twisted WSe$_2$ moir\'{e} structures (Xia et al., Nature 2024; Guo et al., Nature 2025). Its transition temperature is high, reaching a few percent of the Fermi temperature scale. Here, we…
We consider the case of a density-driven metal-superconductor transition in the proximity of an electronic phase separation. In particular we investigate the interplay between superconducting fluctuations and density fluctuations, which…
The orbital symmetries of electron doped iron-arsenide superconductors Ba(Fe1-xCox)2As2 have been measured with x-ray absorption spectroscopy. The data reveal signatures of Fe d electron itinerancy, weak electronic correlations, and a high…
The nematic electronic state and its associated nematic critical fluctuations have emerged as potential candidates for superconducting pairing in various unconventional superconductors. However, in most materials their coexistence with…
Although superconductivity in the vicinity of antiferromagnetic (AFM) instability has been extensively explored in the last three decades or so, superconductivity in compounds with a background of ferromagnetic (FM) spin fluctuations is…
The heavy-fermion system CeCu_{6-x}Au_x exhibits a quantum critical point at x_c = 0.1 separating nonmagnetic and magnetically ordered ground states. The pronounced non-Fermi-liquid behavior at x_c calls for a search for the relevant…
The surprising discovery of tripling the superconducting critical temperature of KFe$_2$As$_2$ at high pressures issued an intriguing question of how the superconductivity in the collapsed tetragonal phase differs from that in the…
The ternary iron arsenide BaFe2As2 becomes superconducting by hole doping, which was achieved by partial substitution of the barium site with potassium. We have discovered bulk superconductivity up to Tc = 38 K in (Ba1-xKx)Fe2As2 with x =…
Using inelastic neutron scattering, we show that the onset of superconductivity in underdoped Ba(Fe$_{1-x}$Co$_{x}$)$_{2}$As$_{2}$ coincides with a crossover from well-defined spin waves to overdamped and diffusive spin excitations. This…
Most iron-based superconductors are characterized by the s+- symmetry of their order parameter, and are expected to go through a transition to the s++ state if enough disorder is introduced. We previously reported the observation of this…
On experimental side, BaFe$_2$As$_2$ without doping has been made superconducting by applying appropriate pressure (2-6 GPa). Here, we use a full-potential linearized augmented plane wave method within the density-functional theory to…
We report synthesis and single crystal measurements of magnetic, transport and thermal properties of single crystalline BaCo$_2$As$_2$ as well as first principles calculations of the electronic structure and magnetic behavior. These results…
We use a quantitative convergent beam electron diffraction (CBED) based method to image the valence electron density distribution in Ba(Fe$_{1-x}$Co$_x$)$_2$As$_2$. We show a remarkable increase in both the charge quadrupole of the Fe…
Superconductivity in alkali-intercalated iron selenide, with T_c's of 30K and above, may have a different origin than that of the other Fe-based superconductors, since it appears that the Fermi surface does not have any holelike sheets…
The crystal structure, anisotropic electrical resistivity and magnetic susceptibility, as well as specific heat results from single crystals of BaFe2As2, BaNi2As2, and BaFeNiAs2 are surveyed. BaFe2As2 properties demonstrate the equivalence…
Resistive and magnetization properties have been measured in BiS$_2$-based samples CeO$_{1-x}$F$_{x}$BiS$_{2}$ with a systematic substitution of O with F (0 $<$ x $<$ 0.6). In contrast to the band structure calculations, it is found that…