Related papers: Superconductivity in multiorbital systems with rep…
Quantum interactions exchanging different types of particles play a pivotal r\^{o}le in quantum many-body theory, but they are not sufficiently investigated from a mathematical perspective. Here, we consider a system made of two fermions…
The formation of Cooper pairs, a bound state of two electrons of opposite spin and momenta by exchange of a phonon [1], is a defining feature of conventional superconductivity. In the cuprate high temperature superconductors, even though it…
Strong correlation effects caused by Hund's coupling have been actively studied during the past decade. Hund's metal, strongly correlated while far from the Mott insulating limit, was studied as a representative example. However, recently,…
Multiorbital Hubbard models host strongly correlated 'Hund's metals' even for interactions much stronger than the bandwidth. We characterize this interaction-resilient metal as a mixed-valence state. In particular it can be pictured as a…
We provide results for the leading superconducting instabilities for a model pertaining to Sr$_2$RuO$_4$ obtained within spin-fluctuation mediated superconductivity in the very weak-coupling limit. The theory incorporates spin-orbit…
We study the fluctuations responsible for pairing in the $d$-wave superconducting state of the two-dimensional Hubbard model at intermediate coupling within a cluster dynamical mean-field theory with a numerically exact quantum impurity…
The mechanism of Cooper pair formation in iron-based superconductors remains a controversial topic. The main question is whether spin or orbital fluctuations are responsible for the pairing mechanism. To solve this problem, a crucial clue…
In many unconventional superconductors the pairing interaction is believed to be mediated by a fluctuating order. Although this is typically taken to be magnetic in origin, the role of other fluctuating orders has recently been considered.…
Cluster dynamical mean field calculations are used to construct the superconducting gap function of the two dimensional Hubbard model. The frequency dependence of the imaginary part of the gap function indicates that the pairing is…
We present the derivation of an ab-initio and parameter free effective electron-electron interaction that goes beyond the screened RPA and accounts for superconducting pairing driven by spin-fluctuations. The construction is based on many…
In heavy-fermion superconductors, it is widely believed that the superconducting gap function has sign-reversal due to the strong electron correlation. However, recently discovered fully-gapped s-wave superconductivity in CeCu2Si2 has…
The one-dimensional SU(4) Hubbard model perturbed by Hund coupling is studied, away from half-filling, by means of renormalization group and bosonization methods. A spectral gap is always present in the spin-orbital sector irrespective of…
We determine the anisotropy of the spin fluctuation induced pairing gap on the Fermi surface of the FeAs based superconductors as function of the exchange and Hund's coupling $J_{H}$. We find that for sufficiently large $J_{H}$, nearly…
A model of superconductivity in layered high-temperature superconducting cuprates is proposed, based on the extended saddle point singularities in the electron spectrum, weak screening of the Coulomb interaction and phonon-mediated…
We propose a microscopical theory of superconductivity in CuO$_2$ layer within the effective two-band Hubbard model in the strong correlation limit. By applying a projection technique for the matrix Green function in terms of the Hubbard…
Spin and charge fluctuations and superconductivity in a recently discovered superconductor Na_xCoO_2*yH_2O are studied based on a multi-orbital Hubbard model. Tight-binding parameters are determined to reproduce the LDA band dispersions…
Near a Mott transition, strong electron correlations may enhance Cooper pairing. This is demonstrated in the Dynamical Mean Field Theory solution of a twofold-orbital degenerate Hubbard model with inverted Hund's rules on-site exchange,…
We propose a possible charge fluctuation effect expected in layered superconducting materials. In the multireference density functional theory, relevant fluctuation channels for the Josephson coupling between superconducting layers include…
Motivated by the recent discovery of superconductivity in infinite-layer nickelates RE$_{1-\delta}$Sr$_\delta$NiO$_2$ (RE$=$Nd, Pr), we study the role of Hund's coupling $J$ in a quarter-filled two-orbital Hubbard model which has been on…
Hund metals are multi-orbital systems with moderate Coulomb interaction, $U$, and sizeable Hund's rule coupling, $J<U$, that aligns the spins in different orbitals. They show strong correlation effects, like very low Fermi-liquid coherence…