22,307 research outputs found
Superconductivity in striped and multi-Fermi-surface Hubbard models: From the cuprates to the pnictides
Single- and multi-band Hubbard models have been found to describe many of the
complex phenomena that are observed in the cuprate and iron-based
high-temperature superconductors. Simulations of these models therefore provide
an ideal framework to study and understand the superconducting properties of
these systems and the mechanisms responsible for them. Here we review recent
dynamic cluster quantum Monte Carlo simulations of these models, which provide
an unbiased view of the leading correlations in the system. In particular, we
discuss what these simulations tell us about superconductivity in the
homogeneous 2D single-orbital Hubbard model, and how charge stripes affect this
behavior. We then describe recent simulations of a bilayer Hubbard model, which
provides a simple model to study the type and nature of pairing in systems with
multiple Fermi surfaces such as the iron-based superconductors.Comment: Published as part of Superstripes 2011 (Rome) conference proceeding
Systematic analysis of a spin-susceptibility representation of the pairing interaction in the 2D Hubbard model
A dynamic cluster quantum Monte Carlo algorithm is used to study a spin
susceptibility representation of the pairing interaction for the
two-dimensional Hubbard model with an on-site Coulomb interaction equal to the
bandwidth for various doping levels. We find that the pairing interaction is
well approximated by {3/2}\Ub(T)^2\chi(K-K') with an effective temperature
and doping dependent coupling \Ub(T) and the numerically calculated spin
susceptibility . We show that at low temperatures, \Ub may be
accurately determined from a corresponding spin susceptibility based
calculation of the single-particle self-energy. We conclude that the strength
of the d-wave pairing interaction, characterized by the mean-field transition
temperature, can be determined from a knowledge of the dressed spin
susceptibility and the nodal quasiparticle spectral weight. This has important
implications with respect to the questions of whether spin fluctuations are
responsible for pairing in the high-T cuprates.Comment: 5 pages, 5 figure
Neutron scattering as a probe of the Fe-pnicitide superconducting gap
Inelastic neutron scattering provides a probe for studying the spin and
momentum structure of the superconducting gap. Here, using a two-orbital model
for the Fe-pnicitide superconductors and an RPA-BCS approximation for the
dynamic spin susceptibility, we explore the scattering response for various
gaps that have been proposed.Comment: 5 pages, 4 figure
Charge transfer statistics of a molecular quantum dot with strong electron-phonon interaction
We analyze the nonequilibrium transport properties of a quantum dot with a
harmonic degree of freedom (Holstein phonon) coupled to metallic leads, and
derive its full counting statistics (FCS). Using the Lang-Firsov (polaron)
transformation, we construct a diagrammatic scheme to calculate the cumulant
generating function. The electron-phonon interaction is taken into account
exactly, and the employed approximation represents a summation of a diagram
subset with respect to the tunneling amplitude. By comparison to Monte Carlo
data the formalism is shown to capture the basic properties of the strong
coupling regime
- …