Related papers: Exploring multichannel superconductivity in ThFeAs…
Temperature dependencies of excess conductivity, Sigma', have been studied in detail for three FeSe_{0.94} textured polycrystalline samples prepared by partial melting and solid state reaction. It was revealed that both Sigma' and its…
We use neutron spectroscopy to determine the nature of the magnetic excitations in superconducting BaFe$_{1.9}$Ni$_{0.1}$As$_{2}$ ($T_{c}=20$ K). Above $T_{c}$ the excitations are gapless and centered at the commensurate antiferromagnetic…
Recent observations of selective emergence (suppression) of superconductivity in the uncollapsed (collapsed) tetragonal phase of LaFe$_2$As$_2$ has rekindled interest in understanding what features of the band structure control the…
The momentum and temperature dependence of the lifetimes of acoustic phonons in the elemental superconductors Pb and Nb was determined by resonant spin-echo spectroscopy with neutrons. In both elements, the superconducting energy gap…
We argue that the pseudogap phase may be an attribute of the non-BCS pairing of quantum-critical, diffusive fermions near the antiferromagnetic quantum critical point. We derive and solve a set of three coupled Eliashberg-type equations for…
We find new mechanism of superconductivity beyond the spin-fluctuation theory, the standard model for unconventional superconductivity in the weak coupling approach, where Kondo fluctuations result in multi-gap superconductivity around an…
The interplay of orbital and spin degrees of freedom is the fundamental characteristic in numerous condensed matter phenomena, including high temperature superconductivity, quantum spin liquids, and topological semimetals. In iron-based…
Resistive, magnetization, torque, specific heat and scanning tunneling microscopy measurements are carried out on the hole heavily doped CsFe$_2$As$_2$ single crystals. A characteristic temperature $T^*\sim13$ K, which is several times…
Increasingly intricate phase diagrams in new classes of superconductors host fascinating interactions between superconductivity, diverse quantum phases, and quantum critical dynamics. The native superfluids, however, often exhibit much…
Since its discovery more than a century ago, superconductivity has been at the epicentre of condensed matter physics research. The electron phonon coupling in conventional superconductors, which obeys BCS theory, causes an attractive…
Ultracold Fermi atoms allow the realization of the crossover from Bardeen-Cooper-Schrieffer (BCS) superconductivity to Bose- Einstein condensation (BEC), by varying with continuity the attraction between fermions of different species. In…
We use inelastic neutron scattering to study the temperature dependence of the low-energy spin excitations in single crystals of superconducting FeTe$_{0.6}$Se$_{0.4}$ ($T_c=14$ K). In the low-temperature superconducting state, the…
We reconsider the long-standing problem of the effect of spin fluctuations on the critical temperature and isotope effect in a phonon-mediated superconductor. Although the general physics of the interplay between phonons and paramagnons had…
Iron pnictides are the only known family of unconventional high-temperature superconductors besides cuprates. Until recently, it was widely accepted that superconductivity is spin-fluctuation driven and intimately related to their…
Superconductors at temperatures below the critical temperature $T_c$ can be modeled as a mixture of Fermi and Bose gases, where the Fermi gas consists of conduction electrons and the Bose gas comprises Cooper pairs. This simple model…
Inelastic light scattering studies on single crystal of electron-doped Ca(Fe0.95Co0.05)2As2 superconductor, covering the tetragonal to orthorhombic structural transition as well as magnetic transition at TSM ~ 140 K and superconducting…
The multiband nature of iron pnictides gives rise to a rich temperature-doping phase diagram of competing orders and a plethora of collective phenomena. At low dopings, the tetragonal-to-orthorhombic structural transition is closely…
Berg, Metlitski and Sachdev, Science 338, 1606 (2012), have shown that the exchange of hidden spin fluctuations by conduction electrons with two orbitals can result in high-temperature superconductivity in copper-oxide materials. We…
Following earlier work on electron or hole liquids flowing through assemblies with magnetic fluctuations, we have recently exposed a marked correlation of the superconducting temperature Tc, for non s-wave pairing materials, with coherence…
We show conclusively that a pseudogap state can arise at $T > T_c$, for reasonable pairing interaction strength, from order parameter fluctuations in a two dimensional minimal model of $d$-wave superconductivity. The occurrence of the…