Terahertz photoresponse of a quantum Hall edge-channel diode

The Teraherz (THz) photoresponse of a two-dimensional electron gas in the quantum Hall regime is investigated. We use a sample structure which is topologically equivalent to a Corbino geometry combined with a cross-gate technique. This quasi-Corbino geometry allows us to directly investigate the THz-induced transport between adjacent edge-states, thus avoiding bulk effects. We find a pronounced photo voltage at zero applied bias, which rapidly decreases when an external current bias is applied. The photo voltage and its dependence on the bias current can be described using the model of an illuminated photodiode, resulting from the reconstruction of the Landau bands at the sample edge. Using the sample as a detector in a Fourier transform spectrometer setup, we find a resonant response from which we extract a reduced effective cyclotron mass. The findings support a non-bolometric mechanism of the induced photo voltage and the proposed edge-channel diode model.Comment: 5 pages, 5 eps-figures, accepted for Phys. Rev.

Exploring factors associated with participation in citizen science among UK museum visitors aged 40-60: A qualitative study using the theoretical domains framework and the capability opportunity motivation-behaviour model

Citizen science has grown as a form of public engagement in science. Middle-aged citizens who are already consuming scientific information should be a potential outreach group. Behaviour change research in citizen science participation among the demographic is lacking. A total of 47 museum visitors aged 40-60 years took part in qualitative questionnaires and semi-structured interviews. Thematic analysis with the aid of theoretical domains framework and capability opportunity motivation-behaviour model revealed eight themes: (1) limited awareness of citizen science; (2) curiosity, competence and other significant characteristics and skills; (3) important beliefs about one's capability; (4) importance of clear project purpose and impacts; (5) interest, enjoyment and incentives; (6) lasting impacts of family upbringing; (7) project details that make participation easy, better project promotion; and (8) the living environment, availability of free time and money. Addressing a maximum number of these factors with behaviour change techniques can improve the likelihood of citizen science participation

Spectroscopy of nanoscopic semiconductor rings

Making use of self-assembly techniques, we demonstrate the realization of nanoscopic semiconductor quantum rings in which the electronic states are in the true quantum limit. We employ two complementary spectroscopic techniques to investigate both the ground states and the excitations of these rings. Applying a magnetic field perpendicular to the plane of the rings, we find that when approximately one flux quantum threads the interior of each ring, a change in the ground state from angular momentum $\ell = 0$ to $\ell = -1$ takes place. This ground state transition is revealed both by a drastic modification of the excitation spectrum and by a change in the magnetic field dispersion of the single-electron charging energy