First observation of antibonding in artificial molecules


When electrons are confined in a flat space, they interact in much the same way as electrons in ordinary atoms by forming into pairs of various energy levels. They can even be made to emit light when they jump from one level to the next, just like electrons in the orbitals in real atoms.

These flat spaces are easily created in a thin semiconductor layer. Because of their similarity with the real thing, these electronic patterns are called “artifical atoms” and they form a kind of periodic table depending on the number of electrons they contain. And get this: put two artificial atoms next two each other and the electrons can tunnel across the gap to form a kind of covalent bond. That makes an artificial molecule.

The chemistry of artificial molecules has received widespread interest in recent years because it is possible to use them to make materials with properties that are otherwise not found in nature. And today, Matt Doty from the Naval Research Labraotry in DC and a few pals announce the first experimental observation of one of these strange properties in artificial diatomic molecules: antibonding.

Doty says that as the distance between two atoms increases, the bond linking them together suddenly switches to an antibond that pushes them apart. Antibonds are never seen in nature. They arise because artificial atoms contain “holes”, the absence of an electron in the structure which can be thought of as positively charged. Doty spotted their effect by looking for the characteristic light signature that an antibond can be made to emit in a magnetic field.

Antibonds could turn out to have useful properties. Doty and pals say molecules containing anitbonds could one day be used to manipulate the spin of passing electrons, a property that could be useful for the emerging field of spintronics.

Let’s wait and see.

Ref: Antibonding Ground States in Semiconductor Artificial Molecules

One Response to “First observation of antibonding in artificial molecules”

  1. ZEPHIR says:

    Antibonds are never seen in nature…, well, it depends, what we’re calling an antibond here. Even the tiny mercury droplets (which are full of free electrons, btw) exhibits a repulsive force at the distance, which prohibits them in merging due their surface tension. Thus is because their merging requires the formation of thin neck with strong negative curvature, which is always source of repulsive force in nature.

    At the moment, such droplet will become very close, a suddenly merging occurs, because the negative gradient will change into positive and the repulsive force will change into attractive one.

    Albeit the mercury dropplet behavior of free electrons isn’t very pronounced in metals, it dictates the behavior of chemical bonds between atoms, which can be interpreted by mercury droplet model in many cases.