Abstract

I will present recent measurements of the energy relaxation length scale in two-dimensional electron gases (2DEGS) [1]. To accomplish this a bar-gate thermometer (BGT) was used to measure the local electron temperature. A BGT is formed by over a symmetric pair of differentially biased bar gates, over which, a thermovoltage develops in response to an elevated electron temperature at its centre. Due to the mesoscopic size of the bar-gates, the analysis of this thermovoltage requires a detailed model including the energy relaxation length scale, the elastic and inelastic power-law exponents for scattering events in the 2DEG, and the geometry of the BGT itself. We develop this model along the lines of Rojek et al. [2]. The result is a good estimate of the local electron temperature, and a measure of the thermal relaxation length scale in the 2DEG itself. Confidence in these results derives from ensuring they are consistent across data sets where the input power and also the electron density in the 2DEG are varied. This work demonstrates a versatile low-temperature thermometry scheme. I will also present our plans to use this thermometry technique to measure the thermal conductivity of mesoscopic 2DEGs themselves, as well as discuss possible future work to expand on what has already been done.

[1] J. Billiald et al, Appl. Phys. Lett. 107, 022104 (2015); http://dx.doi.org/10.1063/1.4926338 [2] S. Rojek and J. König, Phys. Rev. B 90 , 115403 (2014).