5,172 research outputs found
Unconventional Fermi surface instabilities in the Kagome Hubbard Model
We investigate the competing Fermi surface instabilities in the Kagome
tight-binding model. Specifically, we consider onsite and short-range Hubbard
interactions in the vicinity of van Hove filling of the dispersive Kagome bands
where the Fermiology promotes the joint effect of enlarged density of states
and nesting. The sublattice interference mechanism [Kiesel and Thomale, Phys.
Rev. B Rapid Comm., in press.] allows us to explain the intricate interplay
between ferromagnetic fluctuations and other ordering tendencies. On the basis
of functional renormalization group used to obtain an adequate low-energy
theory description, we discover finite angular momentum spin and charge density
wave order, a two-fold degenerate d-wave Pomeranchuk instability, and f-wave
superconductivity away from van Hove filling. Together, this makes the Kagome
Hubbard model the prototypical scenario for several unconventional Fermi
surface instabilities.Comment: 4+e pages, 5 figure
Sublattice Interference in the Kagome Hubbard Model
We study the electronic phases of the kagome Hubbard model (KHM) in the weak
coupling limit around van Hove filling. Through an analytic renormalization
group analysis, we find that there exists a sublattice interference mechanism
where the kagome sublattice structure affects the character of the Fermi
surface instabilities. It leads to major suppression of Tc for d+id
superconductivity in the KHM and causes an anomalous increase of Tc upon
addition of longer-range Hubbard interactions. We conjecture that the
suppression of conventional Fermi liquid instabilities makes the KHM a
prototype candidate for hosting exotic electronic states of matter at
intermediate coupling.Comment: 4+e pages, 3 figure
Anisotropic chiral d+id superconductivity in NaxCoO2 yH2O
Since its discovery, the superconducting phase in water-intercalated sodium
cobaltates NaxCoO2 yH2O (x~0.3, y~1.3) has posed fundamental challenges in
terms of experimental investigation and theoretical understanding. By a
combined dynamical mean-field and renormalization group approach, we find an
anisotropic chiral d+id wave state as a consequence of multi-orbital effects,
Fermi surface topology, and magnetic fluctuations. It naturally explains the
singlet property and close-to-nodal gap features of the superconducting phase
as indicated by experiments.Comment: 4 pages plus references, 5 figure
Pricing forward contracts in power markets by the certainty equivalence principle : explaining the sign of the market risk premium.
In this paper we provide a framework that explains how the market risk premium, defined as the difference between forward prices and spot forecasts, depends on the risk preferences of market players and the interaction between buyers and sellers. In commodities markets this premium is an important indicator of the behavior of buyers and sellers and their views on the market spanning between short-term and long-term horizons. We show that under certain assumptions it is possible to derive explicit solutions that link levels of risk aversion and market power with market prices of risk and the market risk premium. We apply our model to the German electricity market and show that the market risk premium exhibits a term structure which can be explained by the combination of two factors. Firstly, the levels of risk aversion of buyers and sellers, and secondly, how the market power of producers, relative to that of buyers, affects forward prices with different delivery periodsContango; Backwardation; Market price of risk; Electricity forwards; Market risk premium; Forward risk premium; Forward bias; Market power;
Nonclassicality filters and quasiprobabilities
Necessary and sufficient conditions for the nonclassicality of bosonic
quantum states are formulated by introducing nonclassicality filters and
nonclassicality quasiprobability distributions. Regular quasiprobabilities are
constructed from characteristic functions which can be directly sampled by
balanced homodyne detection. Their negativities uncover the nonclassical
effects of general quantum states. The method is illustrated by visualizing the
nonclassical nature of a squeezed state.Comment: Significantly revised version, more emphasis on practical applicatio
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