New insights into the energy levels in Quantum Dots

An electron inside a quantum dot is raised by a photon (green waveform) to a higher energy level. The result is a so-called exciton, an excited state consisting of two electrons and one hole. By emitting a photon (green waveform), the system returns to the ground state (green path). In rare cases, a radiative Auger process takes place (red arrow): an electron stays in the excited state, while a photon of lower energy (red waveform) is emitted. Credit: RUB, Arne Ludwig

Researchers from University of Basel, Bochum, and Copenhagen have gained new insights into the energy states of Quantum Dots (QD).

The scientists confirmed certain energy transitions in QDs that had previously only been predicted theoretically: the so-called radiative Auger process.

For the first time, the researchers demonstrated the connection between the radiative Auger process and quantum optics. They show that quantum optics measurements with the radiative Auger emission can be used as a tool for investigating the dynamics of the single electron.

Using the radiative Auger effect, scientists can also precisely determine the structure of the quantum mechanical energy levels available to a single electron in the Quantum Dot. Until now, this was only possible indirectly via calculations in combination with optical methods. Now a direct proof has been achieved. This helps to better understand the quantum mechanical system.

The group observed the effect not only in quantum dots in indium arsenide semiconductors but also in gallium arsenide semiconductors. (

The researchers report their results in the journal Nature Nanotechnology.

Read more.