24,811 research outputs found
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
Five-Loop Static Contribution to the Gravitational Interaction Potential of Two Point Masses
We compute the static contribution to the gravitational interaction potential
of two point masses in the velocity-independent five-loop (and 5th
post-Newtonian) approximation to the harmonic coordinates effective action in a
direct calculation. The computation is performed using effective field methods
based on Feynman diagrams in momentum-space in space
dimensions. We also reproduce the previous results including the 4th
post-Newtonian order.Comment: 15 pages, 4 figure
Evolution of the neutron resonances in AFe2Se2
Recent experiments on the alkali-intercalated iron selenides have raised
questions about the symmetry of the superconducting phase. Random phase
approximation calculations of the leading pairing eigenstate for a tight-
binding 5-orbital Hubbard-Hund model of AFe2Se2 find that a d-wave (B1g) state
evolves into an extended s{\pm} (A1g) state as the system is hole-doped.
However, over a range of doping these two states are nearly degenerate. Here,
we calculate the imaginary part of the magnetic spin susceptibility
\chi"(q,{\omega}) for these gaps and discuss how the evolution of neutron
scattering resonances can distinguish between them
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