Large thermal Hall coefficient in bismuth

We present a systematical study of thermal Hall effect on a bismuth single crystal by measuring resistivity, Hall coefficient, and thermal conductivity under magnetic field, which shows a large thermal Hall coefficient comparable to the largest one in a semiconductor HgSe. We discuss that this is mainly due to a large mobility and a low thermal conductivity comparing theoretical calculations, which will give a route for controlling heat current in electronic devices.Comment: 4pages, 3 figure

On the problem of comparing graded metamaterials

We use a simple effective model, obtained through the application of high-frequency homogenisation, to tackle the fundamental question of how the choice of gradient function affects the performance of a graded metamaterial. This approach provides a unified framework for comparing gradient functions efficiently and in a way that allows us to draw conclusions that apply to a range of different wave regimes. We consider the specific problem of single-frequency localisation, for which the appropriate effective model is a one-dimensional Schrodinger equation. Our analytic results both corroborate those of existing studies (which use either expensive full-field wave simulations or black-box numerical optimisation algorithms) and extend them to other metamaterial regimes. Based on our analysis, we are able to propose a design strategy for optimising monotonically graded metamaterials and offer an explanation for the lack of a universal optimal gradient function

The sign of charge carriers in luminescent transitions

A thorough treatment of the luminescent mechanisms in high resistivity semiconductors (up to 10 12 ohm cm), has as yet not been satisfactorily established. This is due to the lack of data as is provided by the Hall effect. An AC-AC Hall apparatus has been assembled to determine the sign of charge carriers, and their densities when involved in luminescent transitions. Results of preliminary measurements on CdS will be presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/42575/1/10582_2005_Article_BF01699279.pd