15 research outputs found
Optical properties of the pseudogap state in underdoped cuprates
Recent optical measurements of deeply underdoped cuprates have revealed that
a coherent Drude response persists well below the end of the superconducting
dome. In addition, no large increase in optical effective mass has been
observed, even at dopings as low as 1%. We show that this behavior is
consistent with the resonating valence bond spin-liquid model proposed by Yang,
Rice, and Zhang. In this model, the overall reduction in optical conductivity
in the approach to the Mott insulating state is caused not by an increase in
effective mass, but by a Gutzwiller factor, which describes decreased coherence
due to correlations, and by a shrinking of the Fermi surface, which decreases
the number of available charge carriers. We also show that in this model, the
pseudogap does not modify the low-temperature, low-frequency behavior, though
the magnitude of the conductivity is greatly reduced by the Gutzwiller factor.
Similarly, the profile of the temperature dependence of the microwave
conductivity is largely unchanged in shape, but the Gutzwiller factor is
essential in understanding the observed difference in magnitude between ortho-I
and -II YBaCuO.Comment: 9 pages, 6 figures, submitted to Eur. Phys. J.
Integrated analysis of environmental and genetic influences on cord blood DNA methylation in new-borns
Epigenetic processes, including DNA methylation (DNAm), are among the mechanisms allowing integration of genetic and environmental factors to shape cellular function. While many studies have investigated either environmental or genetic contributions to DNAm, few have assessed their integrated effects. Here we examine the relative contributions of prenatal environmental factors and genotype on DNA methylation in neonatal blood at variably methylated regions (VMRs) in 4 independent cohorts (overall n = 2365). We use Akaike’s information criterion to test which factors best explain variability of methylation in the cohort-specific VMRs: several prenatal environmental factors (E), genotypes in cis (G), or their additive (G + E) or interaction (GxE) effects. Genetic and environmental factors in combination best explain DNAm at the majority of VMRs. The CpGs best explained by either G, G + E or GxE are functionally distinct. The enrichment of genetic variants from GxE models in GWAS for complex disorders supports their importance for disease risk