A breakthrough in material detection is made possible by ‘twistronics’ for bulk systems

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Researchers from the Interdisciplinary Research Group on Low Energy Electronic Systems (LEES) at the Singapore-MIT Alliance for Research and Technology (SMART), a MIT research firm in Singapore, along with the Massachusetts Institute of Technology (MIT) and the National University of Singapore (UXO) ), discovered a new way to control light emission from materials.

Controlling the properties of materials has been the driving force behind most modern technologies – from solar panels, computers, smart vehicles or life-saving hospital equipment. But the properties of materials are traditionally adjusted based on their composition, structure and sometimes size, and most practical devices that produce or generate light use layers of materials of different compositions that can often be difficult to grow.

The breakthrough of SMART researchers and their associates offers a new approach to paradigm shift for adjusting the optical properties of technologically relevant materials by changing the twist angle between stacked films at room temperature. Their discoveries could have a huge impact on a variety of applications in the medical, biological, and quantum information fields. The team explains their research in a paper entitled “Adjustable optical properties of thin films under the control of the torsion angle of the interface”, recently published in a prestigious journal Nano words.

“Numerous new physical phenomena – such as unconventional superconductivity – have recently been discovered by stacking individual layers of atomically thin materials on top of each other at a twisting angle, resulting in what we call moiré superlattices,” says correspondent Professor Silvija Gradečak of the Department of Materials Science. and UXO engineering and chief investigator at SMART LEES. “Existing methods focus on stacking only thin individual layers of film, which is laborious, while our discovery would be applicable to thick films as well – making the material discovery process much more efficient.”

Their research can also be important for the development of basic physics in the field of “twistronics” – the study of how the angle between layers of two-dimensional materials can change their electrical properties. Professor Gradečak points out that the field has so far focused on stacking individual single-layer layers, which requires careful exfoliation and can suffer from relaxation in the twisted state, which limits their practical application. The team’s discovery could make this revolutionary phenomenon associated with twists and turns applicable to thick film systems, which are easy to manipulate and which are industrially relevant.

“Our experiments have shown that the same phenomena that lead to the formation of moiré superlattices in two-dimensional systems can be translated to adjust the optical properties of three-dimensional, hexagonal boron nitride (hBN), even at room temperature,” said Hae Yeon Lee, lead author Labor and PhD in Materials and Engineering candidate at MIT. “We found that both the intensity and color of stacked thick hBN films could be continuously adjusted to their relative twist angles, and the intensity increased more than 40-fold.”

The results of the research open up a new way of controlling the optical properties of thin films outside conventionally used structures, especially for applications in medicine, the environment or information technology.