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Colloquium

Speaker: Muchuan Hua, IUPUI Location: LD 010

Optical refrigeration on CdSe quantum dots

Abstract: In 1929, optical refrigeration (OR) in solids was first proposed by the German physicist Peter Pringsheim. In OR, vibrational energy is removed by spontaneous energy up-conversion photoluminescence (UCPL). Despite of many attempts carried out in different materials, OR in solids was not achieved until 1995, when Epstein and coworkers observed a temperature drop of 0.3 K in Yb3+ doped glass. In 2012, Zhang and his coworkers successfully cooled a CdS nanobelt by 40 K. Their work revealed the possibility of realizing OR in semiconducting nanomaterials and greatly encouraged the research in this field. Here, we are proposing OR on quantum dots (QDs) made of cadmium selenide (CdSe) by utilizing a phonon-annihilation-coupled UCPL process. The possible cooling power calculated based on the data from CdSe QDs (zinc-blende crystal structure) conducted with a recent developed method in our lab will be presented, together with a semi-empirical model developed to help us understand the QDs' PL mechanism and to provide better predictions on the processes involved. Finally, the possibilities and limits of OR in semiconducting quantum dots will be discussed.

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Refreshments at 3:00 pm in the Physics Conference Room LD 154B