21,999 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
The Structure of the Pairing Interaction in the 2D Hubbard Model
Dynamic cluster Monte Carlo calculations for the doped two-dimensional
Hubbard model are used to study the irreducible particle-particle vertex
responsible for pairing in this model. This vertex increases with
increasing momentum transfer and decreases when the energy transfer exceeds a
scale associated with the spin susceptibility. Using an exact
decomposition of this vertex into a fully irreducible two-fermion vertex and
charge and magnetic exchange channels, the dominant part of the effective
pairing interaction is found to come from the magnetic, spin S=1 exchange
channel.Comment: Published version. 4 pages, 4 figure
Theory of plasmon-enhanced high-harmonic generation in the vicinity of metal nanostructures in noble gases
We present a semiclassical model for plasmon-enhanced high-harmonic
generation (HHG) in the vicinity of metal nanostructures. We show that both the
inhomogeneity of the enhanced local fields and electron absorption by the metal
surface play an important role in the HHG process and lead to the generation of
even harmonics and to a significantly increased cutoff. For the examples of
silver-coated nanocones and bowtie antennas we predict that the required
intensity reduces by up to three orders of magnitudes and the HHG cutoff
increases by more than a factor of two. The study of the enhanced high-harmonic
generation is connected with a finite-element simulation of the electric field
enhancement due to the excitation of the plasmonic modes.Comment: 4 figure
Euroscepticism and the use of negative, uncivil and emotional campaigns in the 2019 European Parliament election: A winning combination
Euroscepticism and the use of negative, uncivil and emotional campaigns in the 2019 European Parliament election: A winning combination
Spin Susceptibility Representation of the Pairing Interaction for the two-dimensional Hubbard Model
Using numerical dynamic cluster quantum Monte Carlo results, we study a
simple approximation for the pairing interaction of a two-dimensional Hubbard
model with an on-site Coulomb interaction equal to the bandwidth. We find
that with an effective temperature dependent coupling \Ub(T) and the
numerically calculated spin susceptibility , the d-wave pairing
interaction is well approximated by \frac{3}{2} \Ub^2\chi(K-K').Comment: 5 pages, 7 figure
Evolution of superconductivity in Fe-based systems with doping
We study the symmetry and the structure of the gap in Fe-based
superconductors by decomposing the pairing interaction obtained in the RPA into
s- and d-wave components and into contributions from scattering between
different Fermi surfaces. We show that each interaction is well approximated by
the lowest angular harmonics and use this simplification to analyze the origin
of the attraction in the two channels, the competition between s- and d-wave
solutions, and the origin of superconductivity in heavily doped systems, when
only electron or only hole pockets are present.Comment: 4pp, 2 figures, 2 table
Large tunable photonic band gaps in nanostructured doped semiconductors
A plasmonic nanostructure conceived with periodic layers of a doped
semiconductor and passive semiconductor is shown to generate spontaneously
surface plasmon polaritons thanks to its periodic nature. The nanostructure is
demonstrated to behave as an effective material modeled by a simple dielectric
function of ionic-crystal type, and possesses a fully tunable photonic band
gap, with widths exceeding 50%, in the region extending from mid-infra-red to
Tera-Hertz.Comment: 6 pages, 4 figures, publishe
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