Magnetic-field-induced Stoner transition in a dilute quantum Hall system

In a recent paper [Phys.Rev.B.\textbf{84}, 161307 (2011)], experimental data on spin splitting in the integer quantum Hall effect has been reported in a high mobility dilute 2D electron gas with electron density as low as 0.2 $\times$ 10$^{11}$ cm $^{-2}$. In this work, we show that an excellent \emph{quantitative} description of these data can be obtained within the model of the magnetic-field-induced Stoner transition in the quantum Hall regime. This provides a powerful tool to probe the non-trivial density dependance of electron-electron interactions in the dilute regime of the 2D electron gas

Past-present -future

Double Exposures is a new collaborative venture between Manuel Vason and forty of the most visually arresting artists working with performance in the UK. Ten years after his first, groundbreaking book, Exposures, Vason has produced another extraordinary body of work, which sets out new ways of bridging performance and photography. For Double Exposures, Vason has worked with two groups of artists, using two distinct types of collaboration, to produce a series of double images. Artists who had previously worked with Vason were invited to create two images, one of their own practice and another, where they took on the role of the photographer, shaping an image with Vason’s body. A second group of new collaborators were invited to create a performance, which could be captured in two photographs. All the images exist as doubles – pairs – diptychs. Double Exposures includes commissioned essays on photography and performance by David Bate, David Evans, Dominic Johnson, Lois Keidan, Alice Maude-Roxby, Adrien Sina, Chris Townsend, and Joanna Zylinska and an interview with Helena Blaker. Themes explored include the body, the diptych, documentation, encounters, identity, mediation and the relationship between photography and performance. In photography, a ‘double exposure’ can be accidental or deliberate. Both types permeate Double Exposures, making it Manuel Vason’s most ambitious project to date. Double Exposures collaborators: Aaron Williamson, Áine Phillips, Alexandra Zierle & Paul Carter, Alistair MacLennan, Ansuman Biswas, Brian Catling, David Hoyle, Dickie Beau, Eloise Fornieles, Elvira Santamaría Torres, Ernst Fischer, Florence Peake, Franko B, Giovanna Maria Casetta, Harold Offeh, Helena Goldwater, Helena Hunter, Hugo Glendinning, Iona Kewney, jamie lewis hadley, Joshua Sofaer, Julia Bardsley, Katherine Arianello, Lucille Acevedo-Jones & Rajni Shah, Mad for Real, Marcia Farquhar, Marisa Carnesky, Martin O'Brien, Mat Fraser, Michael Mayhew, Mouse, Nando Messias, Nicola Canavan, Noëmi Lakmaier, Oreet Ashery, Rita Marcalo, Ron Athey, Sinead O'Donnell, Stacy Makishi, The Famous Lauren Barri Holstein, the vacuum cleaner Published with the support of Arts Council England Reviews 'Manuel Vason is to Performance Art what Robert Capa is to war photography.' – Franko B, artist 'Manuel Vason's images exist somewhere between portraiture, performance documentation, and documentary - or perhaps, his images are fashion shots, but the bodies are clothed in performance.' – Tracy Warr, independent curator, editor of The Artist's Body 'Manuel Vason's startling and stylised images, powerfully reproduced in Encounters, violently force bodily abjection into the arena of the sublime. Not since the era of Caravaggio and Bernini has pain been so exquisitely and beautifully rendered - here, through Vason's capacity to connect, via the red-hot wire of aesthetic reduction, to the bodies that wield and convey it.' – Amelia Jones 'Photography stages what it records; and subjects perform on that stage. In this age of the complicit auto-branding of the ‘Selfie’, it’s a relief to be reminded that the self and the camera are less knowable than we might think. In this book Manual Vason’s collaborative photographs along with a range of nimble writers reopen for us all the uncertainties and possibilities, the trapdoors and escape hatches that make the self and the camera such wild companions.' – David Campany, writer, curator and Reader in Photography at the University of Westminster, Londo

The performance document: assimilations of gesture and genre

Artist or activist actions and performances often take place just once and are intended to be experienced live. These actions are recorded and disseminated through photography and video taken from a range of perspectives, from paid-up and pre-briefed “professional” photographers or videographers through to spontaneously taken images by audience members or passers-by. Inevitably “documentation” is never neutral and these records are infused with the stylistic intervention and conventions of the photographer in question. Within our conversation, we locate the performance document as the site of a potential two-way assimilation of gesture and stylistic attributes of diverse photographic conventions. In our co-writing, we track parallel analyses of photographs taken by commercial photographer Françoise Masson of the 1970s actions of artist Gina Pane and the utilization of photographs within the contemporary lens-based practice of Dinu Li, in which gesture and conventions are assimilated and move fluidly backwards and forwards between political propaganda, film, documentary, and domestic photography

Interplay among spin, orbital effects and localization in a GaAs two-dimensional electron gas in a strong in-plane magnetic field

The magnetoresistance of a low carrier density, disordered GaAs based two-dimensional (2D) electron gas has been measured in parallel magnetic fields up to 32 T. The feature in the resistance associated with the complete spin polarization of the carriers shifts down by more than 20 T as the electron density is reduced, consistent with recent theories taking into account the enhancement of the electron-electron interactions at low densities. Nevertheless, the magnetic field for complete polarization, Bp, remains 2-3 times smaller than predicted for a disorder free system. We show, in particular by studying the temperature dependance of Bp to probe the effective size of the Fermi sea, that localization plays an important role in determining the spin polarization of a 2D electron gas.Comment: Published in the Physical Review

Alien Registration- Glidden, Maude A. (Bradley, Penobscot County)

https://digitalmaine.com/alien_docs/9993/thumbnail.jp

Second order resonant Raman scattering in single layer tungsten disulfide (WS2_{2})

Resonant Raman spectra of single layer WS$_{2}$ flakes are presented. A second order Raman peak (2LA) appears under resonant excitation with a separation from the E$^{1}_{2g}$ mode of only $4$cm$^{-1}$. Depending on the intensity ratio and the respective line widths of these two peaks, any analysis which neglects the presence of the 2LA mode can lead to an inaccurate estimation of the position of the E$^{1}_{2g}$ mode, leading to a potentially incorrect assignment for the number of layers. Our results show that the intensity of the 2LA mode strongly depends on the angle between the linear polarization of the excitation and detection, a parameter which is neglected in many Raman studies.Comment: 6 pages, 4 figure

Using the de Haas-van Alphen effect to map out the closed three-dimensional Fermi surface of natural graphite

The Fermi surface of graphite has been mapped out using de Haas van Alphen (dHvA) measurements at low temperature with in-situ rotation. For tilt angles $\theta>60^{\circ}$ between the magnetic field and the c-axis, the majority electron and hole dHvA periods no longer follow the $\cos(\theta)$ behavior demonstrating that graphite has a 3 dimensional closed Fermi surface. The Fermi surface of graphite is accurately described by highly elongated ellipsoids. A comparison with the calculated Fermi surface suggests that the SWM trigonal warping parameter $\gamma_3$ is significantly larger than previously thought