By simply flipping a light switch, a few engineers accidentally made a groundbreaking discovery in quantum electronics. Through a fortunate accident, researchers at University of Chicago and the Pennsylvania State University discovered a new method for drawing quantum mechanical circuits in seconds. While quantum circuits are usually created in advanced nanofabrication facilities, the new light-based technique is so simple that the researchers compared it to an Etch-a-sketch.
The scientists were conducting unrelated research when they realized that the fluorescent lights in their lab were unintentionally changing the electrical properties of strontium titanate, the substrate material they were using in their experiment. It turns out that the material becomes electrically polarized when exposed to light at the particular ultraviolet wavelength that their room’s lights emitted. The electric field from the polarized strontium titanate was leaking into the topological insulator layer, changing its electronic properties. By intentionally focusing beams of light on their samples, the researchers found a way to electronic structures.
In this way, the researchers could “tune” the energy of electrons in the material using light, and without ever having to touch the material itself. They have since used the new technique to draw and erase p-n junctions – one of the central components of a transistor – in a topological insulator for the first time.
“One exciting aspect of this work is that it’s noninvasive” said researcher Nitin Samarth. “Since the electrical polarization occurs in an adjacent material, and the effect persists in the dark, the topological insulator remains relatively undisturbed. With these fragile quantum materials, sometimes you have to use a light touch.”
This new technique could also be applied to other materials to enable electrical tuning for other optical, magnetic and spectroscopic experiments where electrical contacts were previously impossible.
