EPSRC CDT in Metamaterials: Solid State Refrigeration using 2D/Meta materials

The studentship is part of the EPSRC Centre of Doctoral Training in Metamaterials (XM2). Its aim is to undertake world-leading research, while training scientists and engineers with the relevant research skills and knowledge, and professional attributes for industry and academia.

In thermal equilibrium, objects inside a blackbody enclosure absorb and emit radiation at the same rates. However, in some semiconductor devices the emission can be suppressed to below that of the equilibrium level, a phenomena termed "negative luminescence" [1]. One way of achieving NL is to use a type of infrared (IR) LED. When forward biased they emit more IR radiation than they absorb, and so appear hot to an IR observer, but in reverse bias they appear cold. One exciting application of NL devices is for solid state refrigeration [2], where the body to be cooled is placed adjacent to the NL device. The system can then be thought of as a heat pump with photons as the working fluid. Very recently, it has been shown theoretically that the efficiency for cooling can approach the Carnot limit by exploiting optical resonances and near field coupling [3].

The ultimate aspiration of this work is therefore to make the first experimental demonstrate of the theoretically predicted improvement in cooling efficiency by exploiting a hybrid system consisting of 2D materials (e.g. hexagonal boron nitride, black phosphorous) and metamaterial resonant structures [4]. The project, which will involve a mixture of theory, sample processing and experiment, cuts across several XM2 themes and the student will benefit greatly from the expertise and environment of the CDT. As this is a relatively new area, there is the opportunity to produce some truly novel results.

[1] See, for example, G. R. Nash et al, “Long wavelength infrared negative luminescent devices with strong Auger suppression”, J. Appl. Phys. 94, 7300 (2003).

[2] P. Berdahl, “Radiant refrigeration by semiconductor diodes”, J. Appl. Phys. 58, 1369 (1985).

[3] Kaifeng Chen et al, Parthiban Santhanam, and Shanhui Fan, “Near-Field Enhanced Negative Luminescent Refrigeration”, Phys. Rev. Appl. 6, 024014 (2016).

[4] P. Q. Liu, I. J. Luxmoore, S. A. Mikhailov, N. A. Savostianova, F. Valmorra, J. Faist, and G. R. Nash, “Highly tunable hybrid metamaterials employing split-ring resonators strongly coupled to graphene surface plasmons”, Nature Communications 6, 8969 (2015).