A direct leap into terahertz

Highspeed Internet, autonomous driving, the Internet of Things: data streams are proliferating at enormous speed. But classic radio technology is reaching its limits: the higher the data rate, the faster the signals need to be transmitted. Researchers at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) have now demonstrated (DOI: 10.1038/s42005-025-02273-0) that weak radio signals can be efficiently converted into significantly higher frequencies using this material that is just several tens of nanometers thick. And at room temperature, at that. The results open up prospects for future generations of mobile communications and high-resolution sensor technology.

The more data to be transmitted simultaneously, the higher the carrier frequency must be. As a result, research is now delving into the terahertz range. This frequency spectrum lies outside the microwave range currently used and, so far, has been difficult to access technologically. “At present, it’s very inefficient to increase frequencies into the terahertz range and then work with them,” explains Dr. Georgy Astakhov, head of the Quantum Technologies Department of the Institute of Ion Beam Physics and Materials Research at HZDR. This is because the high-frequency signals have to be amplified and stabilized, which until now has required a lot of energy and complex amplifier circuits. “Our approach shows it can be done much more easily.”

Weak signals, strong effect

The team used an ultra-thin film of mercury telluride for their experiment, a material that belongs to the Dirac class of materials. Electrons in this particular material move as though they barely have any mass. They consequently respond extremely fast to electromagnetic fields which makes them highly suited to accelerating or mixing signals.

Interestingly, this material is not a new discovery. Mercury telluride has been utilized in infrared detectors for decades. What is new, however, is the precise control of the very electronic properties that make the material a Dirac material. It opens up possibilities that were previously unthinkable. “The decisive moment in our work was when we clearly saw the signal at room temperature,” says Tatiana Aureliia Uaman Svetikova, doctoral candidate at HZDR and lead author of the study. “It is especially challenging because the signal is easily lost in background noise.” This is the reason why, in the past, comparable experiments have always had to be cooled to extremely low temperatures.

The conversion efficiency that enabled the team to set a new milestone was also astounding. It was over two percent. That is an unusually high value in the terahertz range; the efficiency of such frequency conversions has often been in the area of 0.01 to 0.1 percent in previous approaches.

In order to recognize the signal against the ubiquitous background noise, the team used the ELBE Center for High-Power Radiation Sources at HZDR for its experiments. Here, the TELBE terahertz source and the FELBE free electron laser provide conditions for high-precision experiments. For this particular experiment, the researchers had to precisely combine two terahertz signals at the right angle, with the right intensity, and at the right moment. “That was a massive challenge,” explains Uaman Svetikova. “We had to coordinate the sources very precisely in order to clearly identify the interaction.” It was only this controlled superposition that made it possible to measure the significant transformation.

The results show that Dirac materials could play a core role in future high-frequency technologies. “Dirac materials can efficiently turn weak radio signals into higher terahertz ranges,” explains Astakhov. “That opens up prospects for wireless communication well beyond today’s mobile radio communication, going as far as future 6G and 7G systems, as well as for high-resolution radar and sensor technology.”

However, development activities are still required before it can be applied to building components. The next step the team is planning will be to further refine the structures and transfer them to various material systems. Only then will they be able to explore how well such terahertz mixers can be integrated into real circuits. “We are clearly working in the field of basic research here,” summarizes Astakhov. “But it is a building block that points the way toward compact high-frequency technologies.”

Publication:
T. A. Uaman Svetikova, I. Ilyakov, A. Ponomaryov, T. V. A. G. de Oliveira, C. Berger, L. Fürst, F. Bayer, J.-C. Deinert, G. L. Prajapati, A. Arshad, E. G. Novik, A. Pashkin, M. Helm, S. Winnerl, H. Buhmann, L. W. Molenkamp, T. Kiessling, S. Kovalev, G. V. Astakhov, Highly efficient broadband THz mixing and upconversion with Dirac materials, in Communications Physics, 2025. (DOI: 10.1038/s42005-025-02273-0 )

Additional information:
Dr. Georgy Astakhov | Head of Quantum Technologies
Institute of Ion Beam Physics and Materials Research at HZDR
Tel.: +49 351 260 3894 | E-mail: g.astakhov@hzdr.de

Media contact:
Simon Schmitt | Head
Communications and Media Relations at HZDR
Phone: +49 351 260 3400 | Mob.: +49 175 874 2865 | Email: s.schmitt@hzdr.de

The Helmholtz-Zentrum Dresden-Rossendorf (HZDR) performs – as an independent German research center – research in the fields of energy, health, and matter. We focus on answering the following questions:

• How can energy and resources be utilized in an efficient, safe, and sustainable way?
• How can malignant tumors be more precisely visualized, characterized, and more effectively treated?
• How do matter and materials behave under the influence of strong fields and in smallest dimensions?

To help answer these research questions, HZDR operates large-scale facilities, which are also used by visiting researchers: the Ion Beam Center, the Dresden High Magnetic Field Laboratory and the ELBE Center for High-Power Radiation Sources.
HZDR is a member of the Helmholtz Association and has six sites (Dresden, Freiberg, Görlitz, Grenoble, Leipzig, Schenefeld near Hamburg) with almost 1,500 members of staff, of whom about 700 are scientists, including 200 Ph.D. candidates.