ν=2\nu=2 Bilayer Quantum Hall System in Tilted Magnetic Field

We report on a theoretical study of $\nu=2$ bilayer quantum Hall systems with a magnetic field that has a component parallel to the layers. As in the $\nu=1$ case, interlayer phase coherence is closely coupled to electron correlations and the Aharonov-Bohm phases introduced by a parallel magnetic field can have a strong influence on the ground state of the system. We find that response of a $\nu=2$ system to a parallel field is more subtle than that of a $\nu=1$ system because of the interplay between spin and layer degrees of freedom. There is no commensurate-incommensurate transition as the parallel field is increased. Instead, we find a new phase transition which can occur in fixed parallel field as the interlayer bias potential is varied. The transition is driven by the competition between canted antiferromagnetic order and interlayer phase coherence in the presence of the parallel field. We predict a strong singularity in the differential capacitance of the bilayer which can be used to detect the phase transition.Comment: 11 pages, 6 figures. The final version, to appear in PR

Genomic and phenotypic insights from an atlas of genetic effects on DNA methylation

DNA methylation quantitative trait locus (mQTL) analyses on 32,851 participants identify genetic variants associated with DNA methylation at 420,509 sites in blood, resulting in a database of >270,000 independent mQTLs.Characterizing genetic influences on DNA methylation (DNAm) provides an opportunity to understand mechanisms underpinning gene regulation and disease. In the present study, we describe results of DNAm quantitative trait locus (mQTL) analyses on 32,851 participants, identifying genetic variants associated with DNAm at 420,509 DNAm sites in blood. We present a database of >270,000 independent mQTLs, of which 8.5% comprise long-range (trans) associations. Identified mQTL associations explain 15-17% of the additive genetic variance of DNAm. We show that the genetic architecture of DNAm levels is highly polygenic. Using shared genetic control between distal DNAm sites, we constructed networks, identifying 405 discrete genomic communities enriched for genomic annotations and complex traits. Shared genetic variants are associated with both DNAm levels and complex diseases, but only in a minority of cases do these associations reflect causal relationships from DNAm to trait or vice versa, indicating a more complex genotype-phenotype map than previously anticipated.Molecular Epidemiolog