26 research outputs found
Geometric Suppression of Single-Particle Energy Spacings in Quantum Antidots
Quantum Antidot (AD) structures have remarkable properties in the integer
quantum Hall regime, exhibiting Coulomb-blockade charging and the Kondo effect
despite their open geometry. In some regimes a simple single-particle (SP)
model suffices to describe experimental observations while in others
interaction effects are clearly important, although exactly how and why
interactions emerge is unclear. We present a combination of experimental data
and the results of new calculations concerning SP orbital states which show how
the observed suppression of the energy spacing between states can be explained
through a full consideration of the AD potential, without requiring any effects
due to electron interactions such as the formation of compressible regions
composed of multiple states, which may occur at higher magnetic fields. A full
understanding of the regimes in which these effects occur is important for the
design of devices to coherently manipulate electrons in edge states using AD
resonances.Comment: 4 pages, 2 figure
Elevated CO2 interacts with nutrient inputs to restructure plant communities in phosphorus-limited grasslands
Globally pervasive increases in atmospheric CO2 and nitrogen (N) deposition could have substantial effects on plant communities, either directly or mediated by their interactions with soil nutrient limitation. While the direct consequences of N enrichment on plant communities are well documented, potential interactions with rising CO2 and globally widespread phosphorus (P) limitation remain poorly understood. We investigated the consequences of simultaneous elevated CO2 (eCO2) and N and P additions on grassland biodiversity, community and functional composition in P-limited grasslands. We exposed soil-turf monoliths from limestone and acidic grasslands that have received >25âyears of N additions (3.5 and 14âgâmâ2âyearâ1) and 11 (limestone) or 25 (acidic) years of P additions (3.5âgâmâ2âyearâ1) to eCO2 (600âppm) for 3âyears. Across both grasslands, eCO2, N and P additions significantly changed community composition. Limestone communities were more responsive to eCO2 and saw significant functional shifts resulting from eCO2ânutrient interactions. Here, legume cover tripled in response to combined eCO2 and P additions, and combined eCO2 and N treatments shifted functional dominance from grasses to sedges. We suggest that eCO2 may disproportionately benefit P acquisition by sedges by subsidising the carbon cost of locally intense root exudation at the expense of co-occurring grasses. In contrast, the functional composition of the acidic grassland was insensitive to eCO2 and its interactions with nutrient additions. Greater diversity of P-acquisition strategies in the limestone grassland, combined with a more functionally even and diverse community, may contribute to the stronger responses compared to the acidic grassland. Our work suggests we may see large changes in the composition and biodiversity of P-limited grasslands in response to eCO2 and its interactions with nutrient loading, particularly where these contain a high diversity of P-acquisition strategies or developmentally young soils with sufficient bioavailable mineral P