Related papers: Possible pairing states of the Fe-based supercondu…
The nature of spin-density wave and its relation with superconductivity are crucial issues in the newly discovered Fe-based high temperature superconductors. Particularly it is unclear whether the superconducting phase and spin density wave…
A brief review of optical and Raman studies on the Fe-based superconductors is given, with special emphasis on the competing phenomenon in this system. Optical investigations on ReFeAsO (Re=rare-earth element) and AFe$_2$As$_2$…
We investigate the effects of pairing fluctuations in fermionic superfluids/superconductors where pairing occurs among three species (colors) of fermions. Such color superfluids/superconductors can be realized in three-component atomic…
Superconducting iron chalcogenide FeSe has the simplest crystal structure among all the Fe-based superconductors. Unlike other iron pnictides, FeSe exhibits no long range magnetic order accompanying the tetragonal-to-orthorhombic structural…
We study the superfluid critical temperature in a two-band attractive Fermi system with strong pairing fluctuations associated with both interband and intraband couplings. We focus specifically on a configuration where the intraband…
The theoretical analysis of the Cooper pair susceptibility shows the two-band Fe-based superconductors (FeSC) to support the existence of the phase with nonzero Cooper pair momentum (called the Fulde--Ferrel--Larkin--Ovchinnikov phase or…
Superconducting states that break space-group symmetries of the underlying crystal can exhibit nontrivial spatial modulation of the order parameter. Previously, such remarkable states were intimately associated with the breaking of…
In the correlated electron system with the pseudogap, there are full-gapped domains and Fermi-arced domains coexisting. Those domains are created by the quantum-fluctuated antiferromagnetic fluctuations that generate the short-ranged…
Using a realistic ten-orbital tight-binding model Hamiltonian fitted to the angle-resolved photoemission (ARPES) data on LiFeAs, we analyze the temperature, frequency, and momentum dependencies of quasiparticle interference (QPI) to…
The high-$T_c$ cuprates are possible candidates for d-wave superconductivity, with the Cooper pair wave function belonging to a non-trivial irreducible representation of the lattice point group. We argue that this d-wave symmetry is related…
A model for the coexistence of p-wave superconductivity (SC) and ferroelectricity (FE) is presented. The Hamiltonian of SC sector and FE sector can be diagonalized by using the $so(5)$ and $h(4)$ algebraic coherent states respectively. We…
We propose a two band model for superconductivity. It turns out that the simplest nontrivial case considers solely interband scattering, and both bands can be modeled as symmetric (around the Fermi level) and flat, thus each band is…
We investigate pairing fluctuation effects in a two band fermionic system, where a shallow band in the Bardeen--Cooper--Schrieffer--Bose--Einstein condensation (BCS-BEC) crossover regime is coupled with a weakly interacting deep band.…
We show that, at weak to intermediate coupling, antiferromagnetic fluctuations enhance d-wave pairing correlations until, as one moves closer to half-filling, the antiferromagnetically-induced pseudogap begins to suppress the tendency to…
We report 75As-nuclear quadrupole resonance (NQR) studies on (Ca_4Al_2O_{6-y})(Fe_2As_2) with Tc=27K, which unravel unique normal-state properties and point to unconventional nodeless superconductivity (SC). Measurement of…
We study the electronic structure within a system of phase-decoupled one-dimensional superconductors coexisting with stripe spin and charge density wave order. This system has a nodal Fermi surface (Fermi arc) in the form of a hole pocket…
The antiferromagnetism (AFM) and chiral-d wave superconductivity (SC) in a honeycomb lattice close to an antiferromagnetic (AF) Mott state at half band filling are studied with a t-J model and slave boson mean field theory. The order…
A systematic diagrammatic expansion for Gutzwiller-wave functions (DE-GWF) proposed very recently is used for the description of superconducting (SC) ground state in the two-dimensional square-lattice $t$-$J$ model with the hopping electron…
We studied the effects of isoelectronic Ru substitution at the Fe site on the energy gaps of optimally F-doped SmFeAsO by means of point-contact Andreev reflection spectroscopy. The results show that the SmFe_{1-x}Ru_{x}AsO_{0.85}F_{0.15}…
In iron pnictides, we find that the moderate electron-phonon interaction due to the Fe-ion oscillation can induce the critical d-orbital fluctuations, without being prohibited by the Coulomb interaction. These fluctuations give rise to the…