Bringing quantum wells to light

Henri Bachau, from the University of Bordeaux and Lampros Nikolopoulos, from Dublin City University, have been working together on quantum physics for more than ten years.
After having jointly participated to several COST European programmes, their collaboration is now laureates of the Embassy’s 2015 Ulysses funding scheme.

Electrons confined in a quantum well

Their research project works on the theoretical study of electrons confined in a quantum well and their interactions with a laser field. As Henri Bachau explains, “quantum wells are at the origin of many semiconductor devices. To give an example of a quantum well at our scale, you have to imagine a spherical cavity with a marble in it: the marble is said to be confined. At rest, the marble is positioned at the base of the well.

When the marble is given speed (i.e energy), the marble acquires a periodic movement and possibly can come out from the hollow.

Let’s come back to the microscopic scale, more precisely, the nanometric scale (1 nanometer = 10-9metres). The marble is the electron; the hollow the quantum well (in practice, composed of layers from different materials). The electron’s dynamics are ruled by quantum mechanics.”

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Computerized model of a quantum well

How to describe what is going on in the well?

“When there are several electrons in a quantum well, each of them interacting with the others, the theoretical description of the electronic dynamics in the well is a complex issue that needs the use of sophisticated numerical methods as well as powerful calculators.

A typical example of dynamic electronic is when two electrons are prepared to be in a state called “metastable”. In this configuration, the electrons are either confined or trapped in the well for a certain time (generally, more than one picosecond, that is to say 10-12 seconds). One of the electrons then is emitted from the quantum well. This is called the metastable state’s “lifetime” and this important parameter can be accessed through the study of the interaction between a laser and the electrons trapped in the well. This kind of study is the perfect example of a problematic that raises fundamental issues upstream and important fundamental applications downstream as semiconductors’ properties are closely linked with their electronic structures’ characteristics.”

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Dr Nikolopoulos and Dr Bachau (from left to right)

To find out more

Henri Bachau is a Research supervisor at the Centre National de la Recherche Scientifique (CNRS) and works in the Centre des Lasers Intenses et Application (Centre for Intense Lasers and Application) of the University of Bordeaux. Lampros Nikolopoulos is a “SFI Stokes Lecturer” at Dublin City University.

Henri Bachau and Lampros Nikolopoulos worked together on actions COST CUSPFEL (2008-2012) et Xlic (2013-2017)

Published on 06/08/2015

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