Superconductors, ferromagnetism, and charge density waves are all quantum states that could enhance the functionality of electronic devices. However, doing so requires the development of transistors capable of controlling these quantum states. Although such special transistors have been around for some time, because they rely on electrochemistry, they aren’t very efficient. That’s why their use hasn’t evolved beyond the demonstration phase and, over time, they have been pretty much forgotten about. Yet, for Justin Ye, a researcher at the University of Groningen in the Netherlands, these designs could hold the key to enabling quantum-capable transistors. With the support of the EU-funded Ig-QPD (Ion-gated Interfaces for Quantum Phase Devices) project, Ye has dusted off and reworked these original designs. “In a sense, this project is works in reverse,” he says. “We took the original transistor design based on electrochemistry and, by playing with the so-called ionic gating, showed how it could be transformed into a superconductor.” As a result, the project has advanced the state-of-the-art in technology capable of inducing and controlling quantum phase using field effect. It also took this one step further, applying the controlled quantum phases as electronic functionalities for electronic devices.
Controlling the quantum phase transition
The key objective of the Ig-QPD project was to successfully control the quantum phase transition in electronic devices. To do this, researchers built devices using ion-gated transistors. “This makes it possible to reach the capacity needed to induce quantum phase, such as superconductivity,” explains Ye. Dr Ye explains that superconductivity is the phenomenon where a charge moves through a material without resistance. In doing so, it allows electrical energy to be transferred between two points with perfect efficiency and losing nothing to heat. This method also allows researchers to mix different properties of quantum phase. “For example, using a magnetic ionic liquid we are able to control ferromagnetism,” adds Ye. According to Ye, the team succeeded in developing a highly efficient, tuneable interface with ion-movement-mediated gating. This could serve as a platform for new electronic devices, allowing them to use field effect to control quantum phase transitions. The project also worked on a broad range of 2D materials, including transition metal dichalcogenides. Here, researchers discovered so-called Ising superconductivity in molybdenum disulfide (MoS2), which is arguably the most resilient state against an applied magnetic field.
Making a big impression
Although the project is still a work-in-progress, it is already making a big impression in the scientific field. “Our work represents an exciting new field of research that is attracting the attention of research groups around the world,” notes Ye. “This can be seen in the many leading scientific journals that have published our findings on realising the quantum phase device.” The project also succeeded in supporting the research of six Ph.D. students and two postdocs. Two of the Ph.D. students have since graduated and the two postdocs have found academic work in a related field. “In addition to the ground-breaking research coming out of this project, Ig-QPD also played an important role in providing the training and growth for these young scientists who represent the future of quantum phase devices,” adds Ye.
Ig-QPD, quantum phase device, quantum phase transition, electronic devices, superconductors, quantum states, transistors, electrochemistry, field effect