Researchers at ETH Zurich have succeeded for the first time in trapping excitons—quasiparticles consisting of negatively charged electrons and positively charged holes—in a semiconductor material using controllable electric fields. The new technique is important for creating single photon sources as well as for basic research.
In semiconductor materials, electric current can be conducted both by electrons and by positively charged holes, or missing electrons. Light hitting the material can also excite electrons to a higher energy band, leaving behind a hole in the original band. Through electrostatic attraction, the electron and the hole now combine to create a so-called exciton, a quasiparticle that, as a whole, behaves like a neutral particle. Because of their neutrality, so far is has been difficult to hold excitons at a specific point inside a material.
A team of scientists led by Ataç Imamoğlu, professor at the Physics Department, Puneet Murthy, postdoc in his group, and David Norris, professor at the Department of Mechanical and Process Engineering, have now succeeded for the first time in trapping excitons in a tiny space using controllable electric fields, and also demonstrating the quantization of their motion. The researchers hope that their results, recently published in the scientific journal Nature, will lead to progress towards applications in optical technologies as well as to new insights into fundamental physical phenomena.
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