The Potential of the "Dark Side" of Electronics Revealedš¤
- katerinabiryukova
- Oct 13, 2025
- 3 min read
š¬š³Researchers at the Okinawa Institite of Science and Technology (OIST) recently discovered a novel method to directly observe the behavior of "dark excitons" in one-atom thick materials. A dark exciton is a type of particles studied in quantum physics that forms when energy is applied to an atom.
This is a big step forward as understanding and manipulating these particles could revolutionize solar cellsāļø, sensorsš©», LEDsš” and even allow the solution of complex problems beyond the capabilities of today's computers (quantum computingš). The advantage of these over other quantum particles is that they have a longer lifetime, meaning that they can store information for longer periods of timešµā³ļø, and that they are more resistant to environmental factors like temperature - a key property when making practical devicesš”.
Where Do Dark Excitons Come From?
(using tennis ball analogyš„)
In their neutral state, electrons in an atom travel around the nucleus in orbits, kind of like planets do around the Sun.
When light hits the atomā”, some electrons from the outermost orbit get excited and, like a tennis ball, jump up to a more outer orbit (which previously had no electrons in it). Ā As an electron is a negative particle, when it jumps, it leaves behind a positive "hole" - like a shadow from the tennis ball - in its place.
This hole, due to the attraction between a positive and a negative charge, gets bound to the electron (the ball) that jumped out of it - this pair is known as an "exciton".
Another thing to mention is that, unlike in real life, there is a condition that needs to be satisfied for the tennis ball to fall back onto the ground and cover its shadow. Electrons (balls) and holes (shadows) both have certain properties that can have different values associated with them: spin and momentum.
If both of those properties match for an electron and a hole in an exciton, they recombine, return to their original position (the ball falls back down and cancels the shadow) and emit LIGHT = these guys are "bright excitons". But if one or both properties of an electron and a hole do not match, they cannot recombine (the ball stays in the air instead of falling down) - these are the "dark excitons".
This mismatch is what gives the dark excitons their longer lifetime and makes them less prone to be affected by the environment.
"Superpowers" of Scientists
The final stage is manipulating the particles - and this is where the magical powers of scientists come in. They can use a specific type of light (circularly polarized) to produce "bright excitons" at specific points. Then, these bright excitons get rapidly scattered around in the material, which can make the electrons change their momentum. Since the electrons and the holes in the excitons now have different momentum, they change into dark excitons. Dark excitons live for long periods of time and can thus preserve the information.
Where Does the Journey in the Dark Lead to?
One notable feature of the discoveries within this field is the timeframe in which all of the above-mentioned processes happen: the bright excitons become dark within a picosecond - this is one trillionth of a second! The device capable of producing such images is TR-APRES (time- and angle resolved photoemission spectroscopy) microscope.
While the existence of dark excitons has been aknowledged in the world of quantum physics for a while, this year the OIST researchers were able, for the first time in history, to measure the momentum, spin and distribution of electrons and holes in a material at the same time! This innovation is a large leap forward in information storage technologies. It is also a foundation stone for the field of "dark valleytronics".
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