Related papers: Spin fluctuations and unconventional pairing in KF…
We present a systematic analysis on the basis of ab initio calculations and many-body perturbation theory for clarifying the dominant fluctuation in complex charge-spin-orbital coupled systems. For a tight-binding multiband model obtained…
Superconductivity in lanthanide- and actinide-based heavy-fermion metals can have different microscopic origins. Among others, Cooper pair formation based on fluctuations of the valence, of the quadrupole moment or of the spin of the…
Spin fluctuations are a leading candidate for the pairing mechanism in high temperature superconductors, supported by the common appearance of a distinct resonance in the spin susceptibility across the cuprates, iron-based superconductors…
It has been proposed that Sr_2RuO_4 exhibits spin triplet superconductivity mediated by ferromagnetic fluctuations. So far neutron scattering experiments have failed to detect any clear evidence of ferromagnetic spin fluctuations but,…
We demonstrate that the differential conductance, $dI/dV$, measured via spectroscopic imaging scanning tunneling microscopy in the doped iron chalcogenide FeSe$_{0.45}$Te$_{0.55}$, possesses a series of characteristic features that allow…
The spin susceptibility of strongly correlated Sr$_2$RuO$_4$ is known to display a rich structure in reciprocal space, with a prominent peak at ${\bf Q}_i$=$(0.3,0.3,0)$. It is still debated if the resulting incommensurate spin-density-wave…
Polarized inelastic neutron scattering experiments were performed to study magnetic excitations in the normal and superconducting phases of Co-underdoped BaFe$_2$As$_2$, which exhibits coexistence of antiferromagnetic order and…
Motivated by recent experimental investigations of the isovalent doping iron-based superconductors LaFe(AsxP1-x)O1-yFy and NdFe(AsxP1-x)O1-yFy we theoretically study the correlation between the local lattice structure, the Fermi surface,…
Pairing symmetry in the superconducting state coexisting with antiferromagnetic order is studied based on a microscopic theory. We calculate the linearized Eliashberg's equation within the random phase approximation in the Hubbard model…
We investigate the doping dependence of the magnetic excitations in two-superconducting-dome-system LaFeAsO1-xDx. Using inelastic neutron scattering, spin fluctuations at different wavenumbers were observed under both superconducting domes…
We study spin resonance in the superconducting state of recently discovered alkali-intercalated iron selenide materials A_xFe_(2-y)Se_2 (A=K,Rb,Cs) in which the Fermi surface has only electron pockets. Recent angle-resolved photoemission…
The pseudogap metal phase of the hole-doped cuprate superconductors has two seemingly unrelated characteristics: a gap in the electronic spectrum in the `anti-nodal' region of the square lattice Brillouin zone, and discrete broken…
We study spin fluctuations in the spiral phase of the two-dimensional Hubbard model at low doping on the basis of the spin-particle-hole coherent-state path integral. In the strong correlation limit, we obtain an analytical expression of…
We performed nuclear magnetic resonance (NMR) measurements to investigate the evolution of spin-density-wave (SDW) and superconducting (SC) states upon electron doping in CaFe_{1-x}Co_{x}AsF, which exhibits an intermediate phase diagram…
We review the normal and superconducting state properties of the unconventional triplet superconductor Sr$_2$RuO$_4$ with an emphasis on the analysis of the magnetic susceptibility and the role played by strong electronic correlations. In…
We investigate superconductivity in a two-band system with an electron- and hole-like band, where one of the bands is away from the Fermi level (or incipient). We argue that the incipient band contributes significantly to spin-fluctuation…
Despite of many experimental and theoretical efforts, the pairing symmetry of superconductivity in Sr$_2$RuO$_4$ remains undecided. The accidentally degenerate $d_{x^2-y^2}+ig$ is consistent with most current experiments and seems to be one…
We report $^{75}$As nuclear magnetic resonance measurements on single crystals of RbFe$_{2}$As$_{2}$ and CsFe$_{2}$As$_{2}$. Taking previously reported results for KFe$_{2}$As$_{2}$ into account, we find that the anisotropic electronic…
The spin-fluctuation based pairing mechanism has proven successful in explaining the pairing symmetries due to Fermi surface nesting of both cuprates and iron-based materials. In this work, we study signatures of a spin-fluctuation mediated…
The explanation of heavy-fermion superconductivity is a long-standing challenge to theory. It is commonly thought to be connected to non-local fluctuations of either spin or charge degrees of freedom and therefore of unconventional type.…