Cooling a semiconductor with polaritons

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Science  29 May 2015:
Vol. 348, Issue 6238, pp. 986
DOI: 10.1126/science.348.6238.986-b

Shining light onto a solid to cool it may seem counterintuitive, because the light will temporarily increase the solid's energy. To go back to its low-energy state, the solid may then emit photons more energetic than the ones it absorbed initially, effectively lowering its temperature. Such cooling methods are well established, but place stringent requirements on the material being cooled. Klembt et al. show that exciton-polaritons, exotic part-photon, part-exciton quasi-particles, can be used to cool a semiconductor microcavity. The cooling mechanism depends on the ability of the polaritons to absorb the energy of lattice vibrations and shortly thereafter to leave the solid as light. At low enough laser power, this process overpowers a competing heating process in which two photons are absorbed simultaneously.

Phys. Rev. Lett. 114, 186403 (2015).

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