Posted: April 1, 2009

Quantum dots behave differently than natural atoms when forming molecules

(Nanowerk News) A study has demonstrated that the behaviour of quantum dots is different from that posited by atomic physics so far, and this is due to the spin of the electron. This is one of the findings of the theoretical study carried out by Juan Ignacio Climente, a Ramón y Cajal researcher in the Department of Physical and Analytical Chemistry at the Universitat Jaume I (UJI), and other researchers from the National Research Council of Canada. The study has been recently published in Physical Review Letters ("Antibonding Ground States in InAs Quantum-Dot Molecules").
The study reveals that the behaviour of quantum dots (sort of artificial atoms created with semiconductor materials) is different from that of natural atoms in similar conditions, when they combine to form molecules.
The experiments, conducted by the staff of the Naval Research Laboratory in Washington, have proved that quantum dots that use holes (electrons with a positive charge and a larger mass) instead of electrons (which have a negative charge) achieve an antibonding molecular ground state, in contrast to natural atoms, which need an extra supply of energy to achieve this state.
The new contribution enables researchers to influence the behaviour of quantum dots, and to give them convenient properties. That is why the research described marks a breakthrough in the study of fundamental physics, since it makes it possible to examine in the laboratory situations that could not be studied using natural atoms.
Today, quantum dots are used in optoelectronics for manufacturing lasers that emit light at a frequency that is in the infrared spectrum, thus obtaining greater efficiency; in biomedicine, as biomarkers, to offer clearer images; and in energy-efficient transistors, which are charged with only one electron.
The study results have served to open new research lines. Although it is still too early to know all the possible applications, there may be some in fields such as solar energy, where there is experimentation with third-generation panels (more efficient and economical than those used to date); computer memory devices with a higher density that consume less; treatment of diseases such as cancer, for which a quantum dot may be injected into the body in such a way that it finds the tumoral cell and is then heated with infrared light until the cell is killed; and in new lighting systems offering greater efficiency.
Source: Universitat Jaume I
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