Scientists have succeeded in combining for the very first time two exciting types of materials: an ultra-thin semiconductor only one atom thick; and a superconductor, capable of conducting electricity with zero resistance.
These two materials have unusual and fascinating properties, and by combining them through a delicate laboratory fabrication process, the team behind the research hopes to open up all kinds of new applications in classical and quantum physics.
Semiconductors are the key to the electrical gadgets that dominate our lives, from TVs to phones. What makes them so useful compared to regular metals is that their electrical conductivity can be adjusted by applying voltage to them (among other methods), making it easy to turn a current flow on and off.
Here, a single layer of semiconductor molybdenum disulfide (MoS2) was extracted and added to the manufacturing process.
Then we have superconductors – capable of transferring an electrical charge with perfect efficiency and without any heat loss, at a certain temperature (usually extremely low).
In this setup, a superconductor called rhenium molybdenum (MoRe) has been added to the device, and the researchers expect to observe completely new physical phenomena from their combined materials.
“In a superconductor, electrons organize themselves in pairs, like partners in a dance – with strange and wonderful consequences, such as the passage of electric current without resistance”, explains physicist Andreas Baumgartner of the University of Basel in Swiss.
“In the semiconductor molybdenum disulfide, on the other hand, the electrons perform a completely different dance, a strange solo routine that also incorporates their magnetic moments. Now we would like to find out which new and exotic dances the electrons are tuning into. if we combine these materials. “
Ultrafine semiconductors like the one used here are a hot research topic for researchers right now: they can be stacked together to form entirely new synthetic materials known as van der Waals heterostructures.
These structures have many potentially innovative uses, such as the ability to control electronic magnetism with electric fields. Much of that potential is still theoretical, however, as scientists just don’t yet know what effects they’re going to get and what devices they might be able to make. This is why successfully creating this last combination is so important.
In the latter setup, the team found evidence of a strong coupling (interactions known as the proximity effect) between the semiconductor layer and the superconductor, when the materials were cooled to just above zero. absolute (-273.15 ° C or -459.67 ° F).
“The strong coupling is a key element in the new and exciting physical phenomena that we expect to see in such van der Waals heterostructures, but which we have never been able to demonstrate,” explains physicist Mehdi Ramezani, of the University of Basel.
Establishing this semiconductor-superconductor bond is not easy – as you would expect, given that no one has done it before. The semiconductor is placed in a sandwich, with insulating layers above and below, while holes etched into the top of the insulating layer provide access to the electrical contact.
The superconducting material fills in the gaps left by the holes, and the process is completed inside a nitrogen-filled glove box to protect the finished system from damage. Remote controlled micromanipulators are used to complete the fabrication, under an optical microscope.
With manufacturing now complete, tests and experiments can begin – and have already started – in refrigerators cooled to near absolute zero. In addition, the researchers believe they can use the same technique to work with other semiconductors in the future, further increasing its potential.
“Our measurements show that these hybrid single-layer semiconductor components are indeed possible – perhaps even with other more exotic contact materials that would pave the way for further information,” says Baumgartner.
The research was published in Nano letters.