What Is This

What is this?

What Is This

The image shows an artist’s (Peter Allen) rendition of the energy profile of a highly charged InGaAs quantum post embedded in a quantum well. InGaAs quantum posts are nanostructures that confine charge to small regions within GaAs crystals grown by molecular beam epitaxy at UCSB. They are approximately cylindrical in shape, with heights and diameters of ~30 nm. The figure shows a single quantum post containing six electrons. Strong Coulomb repulsion between electrons in the post prevents further electrons from entering, causing electrons to fill the surrounding quantum well. The high electron density (yellow) in the post pushes the energies of its conduction band up through the electronic Fermi level, much like a volcano pushing itself out from under the ocean.

In the experiment, terahertz radiation is applied to the quantum post/well system in this highly charged state. Terahertz radiation is absorbed by electrons in the posts, which pushes them into the well, effectively “ionizing” electrons from the quantum posts. This provides a unique solid state system in which to study the physics of ionization, at ionization energies much lower than those naturally present in real atoms.

Credit: “Terahertz ionization of highly charged quantum posts in a perforated electron gas,” Morris, C. M., Stehr, D., Kim, H. C., Truong, T., Pryor, C., Petroff, P. M., and Sherwin, M. S. Nano Letters Articles ASAP.