Upper bounds on collective light-matter coupling strength with plasmonic meta-atoms

Ultrastrong coupling between optical and material excitations is a distinct regime of electromagnetic interaction that enables a variety of intriguing physical phenomena. Traditional ways to ultrastrong light-matter coupling involve the use of some sorts of quantum emitters, such as organic dyes, quantum wells, superconducting artificial atoms, or transitions of two-dimensional electron gases. Often, reaching the ultrastrong coupling domain requires special conditions, including high vacuum, strong magnetic fields, and extremely low temperatures. Recent report indicate that a high degree of light-matter coupling can be attained at ambient conditions with plasmonic meta-atoms -- artificial metallic nanostructures that replace quantum emitters. Yet, the fundamental limits on the coupling strength imposed on such systems have not been identified. Here, using a Hamiltonian approach we theoretically analyze the formation of polaritonic states and examine the upper limits of the collective plasmon-photon coupling strength in a number of dense assemblies of plasmonic meta-atoms. Starting off with spheres, we identify the universal upper bounds on the normalized collective coupling strength $g/\omega_0$ between ensembles of plasmonic meta-atoms and free-space photons. Next, we examine spheroidal metallic meta-atoms and show that a strongly elongated meta-atom is the optimal geometry for attaining the highest value of the collective coupling strength in the array of meta-atoms. The results could be valuable for the field of polaritonics studies, quantum technology, and modifying material properties

Summary statistics of UK Biobank blood pressure genome-wide association studies (GWAS) using 337,422 unrelated white European individuals

Three blood pressure traits were analysed: systolic blood pressure (SBP), diastolic blood pressure (DBP) and pulse pressure (PP; the difference between SBP and DBP). Mean SBP and DBP values from automated values were calculated. After calculating blood pressure values, SBP and DBP were adjusted for medication use by adding 15 and 10 mm Hg to their values, respectively, for individuals reported to be taking blood pressure–lowering medication.For the UK Biobank genome-wide association studies (GWAS), we performed linear mixed model (LMM) association testing under an additive genetic model of the three continuous, medication-adjusted blood pressure traits (SBP, DBP, PP) for all measured and imputed genetic variants (Data Field-22828) with minor allele frequency (MAF) >=1% and imputation score>=0.3 in dosage format using the BOLT-LMM (v2.4.1) software. Covariates were age, age2, sex, BMI, genotyping array and 10PCs. Genomic inflation was not applied to the GWAS summary statistics.Sample QC was described below:We included up to 337,422 individuals from UK Biobank for the purpose of this project. We followed UK Biobank sample-based quality control criteria (Nature 2018;562:203-209); excluded were samples/individuals based on the following criteria: (i) outliers in heterozygosity and missingness, (ii) self-reported gender not consistent with genetic data inferred gender (ii) sample call rate (computed using probesets internal to Affymetrix