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Motivated by the experimental results of Willett et al [Phys.Rev. Lett. 78, 4478 (1997)] we develop a magnetotransport theory for the response of a two-dimensional electron gas (2DEG) in the fractional quantum Hall regime near Landau level filling factor ν = 1/2 to the surface acoustic wave (SAW) in the presence of an added periodic density modulation. We assume there exists a composite fermion Fermi surface (CF-FS) at ν = 1/2, and we show that the deformation of the circular CF-FS due to the density modulation can be at the origin of the observed transport anomalies for the experimental conditions. Our analysis is carried out particularly for the nonlocal case which corresponds to the SAW experiments. We introduce a new model of a deformed CF-FS. The model permits us to explain anomalous features of the response of the modulated 2DEG to the SAW near ν = 1/2 : namely, the nonlinear wave vector dependence of the electron conductivity, the appearance of peaks in the SAW velocity shift and attenuation and the anisotropy of the effect, all of which originate from contributions to the conductivity tensor due to the regions of the CF-FS, which are flattened by the applied modulation.

Metal atoms adsorbed on few-layer graphenes condense to form nanometer-size droplets whose growth is size limited by a competition between the surface tension and repulsive electrostatic interactions from charge transfer between the metal droplet and the graphene. For situations where the work-function mismatch is large and the droplet surface tension is small, a growing droplet can be unstable to a family of shape instabilities. We observe this phenomenon for Yb deposited and annealed on few-layer graphenes and develop a theoretical model to describe it by studying the renormalization of the line tension of a two-dimensional droplet by repulsive interparticle interactions. Our model describes the onset of shape instabilities for nanoparticles where the growth is size limited by a generic repulsive potential and provides a good account of the experimentally observed structures for Yb on graphene. Metal atoms adsorbed on few-layer graphenes condense to form nanometer-size droplets whose growth is size limited by a competition between the surface tension and repulsive electrostatic interactions from charge transfer between the metal droplet and the graphene. For situations where the work-function mismatch is large and the droplet surface tension is small, a growing droplet can be unstable to a family of shape instabilities. We observe this phenomenon for Yb deposited and annealed on few-layer graphenes and develop a theoretical model to describe it by studying the renormalization of the line tension of a two-dimensional droplet by repulsive interparticle interactions. Our model describes the onset of shape instabilities for nanoparticles where the growth is size limited by a generic repulsive potential and provides a good account of the experimentally observed structures for Yb on graphene. Disciplines Physical Sciences and Mathematics | Physics

Local geometry of the Fermi surface: and high-frequency phenomena in metals I Natallya A. Zimbovskaya.p. cm. 1ncludes bibliographical references and index.