idw – Informationsdienst Wissenschaft
Nachrichten, Termine, Experten
Nachrichten, Termine, Experten
idw - Informationsdienst
Wissenschaft
Quantum materials are a fascinating platform for future technologies, as they host a variety of exotic phenomena beyond the reach of classical physics. Among them, van der Waals heterostructures stand out: They are created by stacking different two-dimensional layers that can be only one atom thick. These structures are remarkably easy to manipulate, offering unprecedented tunability and a vast realm for exploration. A team from the Max-Planck-Institute for the Structure and Dynamics of Matter (MPSD) and Columbia University has found that van der Waals heterostructures can naturally serve as cavities for long-wavelength terahertz (THz) light. This work has been published in Nature Physics.
Light is a very effective way to probe the properties of materials. By looking at how much light is transmitted through a material, scientists can gain fingerprints of the phase of a material, how the electrons and atoms are ordered, and why this ordering process occurs. Electrical devices made of van der Waals heterostructures are typically micrometers in size- about the width of a human hair. While this is advantageous for future applications, where small, densely packed circuits are desirable, it makes spectral measurements that use low-energy light to investigate their properties, challenging. This is because the relevant wavelength of THz light is far larger than the micron-sized samples. This led the team of scientists to develop a new chip-scale circuitry, based on PI- James McIver’s postdoctoral work. This circuitry confines light to smaller than the light’s wavelength—overcoming the size mismatch between the light and the material. With this circuitry, it is then finally possible to measure the absorption of light in the THz-regime.
But when measuring the absorption in a very simple structure, made up only of two active layers (a single sheet of carbon atoms called graphene, forming a parallel plate capacitor with a slightly thicker sheet of carbon atoms, graphite), the team was in for a surprise. While graphene is one of the most well-understood van der Waals materials, the way the graphene confines light and interacts with the graphite layer, was not expected. Both layers form a cavity. “Traditionally, optical cavities are formed by two parallel mirrors that trap light, allowing it to bounce back and forth many times. Placing a material inside such a cavity enables strong interactions between the trapped light and the material, often revealing new physics that occurs due to this mixture of light and matter,” explains James McIver, group leader at MPSD and PI of the team. “We found that van der Waals heterostructures don’t require external mirrors. The edges of the tiny samples themselves act as reflective boundaries. This opens exciting opportunities because these cavity effects can actually be used to control the properties of the material,” elaborates Hope Bretscher, one of the lead authors of the study, and adds: “In our newly formed cavity, the interaction between the two active layers in the material was so strong – it entered what is called the ‘ultrastrong coupling’ regime.”
These results are very exciting for two reasons. First, the team established the capability to perform spectroscopic investigations of these van der Waals heterostructures on the energy scale of their emergent quantum phases, thereby introducing a unique approach to probing their material properties. They further showed that the extreme confinement of light could in principle allow the material to be tuned by quantum vacuum fluctuations under specific device configurations. These fluctuations in energy happen all around us, but are very weak in free space and typically can be ignored. When the light matter coupling is increased to the degree that the team found, the quantum materials and the quantum fluctuations may act in concert with each other.
Gunda Kipp, co-first author of the study sees a lot of potential for future experiments: “We found that the light-matter coupling was so enhanced, that it may be possible that in the future quantum vacuum fluctuations could even enable the creation of new states of matter.”
These findings demonstrate how exploring new regimes often leads to observations with impactful outcomes. In particular, the use of light to study and control these highly tunable materials could be used to design electronic devices for a range of applications; from highly sensitive single photon detectors, to new superconductors, or other ways to build computers. The research in this regard is just beginning.
Gunda Kipp guna.kipp@mpsd.mpg.de
Hope Bretscher hope.bretscher@mpsd.mpg.de
James McIver james.mciver@mpsd.mpg.de
https://www.nature.com/articles/s41567-025-03064-8
Standing waves of terahertz light are confined in conductive layers of a van der Waals heterostructu ...
Copyright: Brad Baxley
Merkmale dieser Pressemitteilung:
Journalisten, Studierende, Wissenschaftler
Physik / Astronomie, Werkstoffwissenschaften
überregional
Forschungsergebnisse
Englisch
Sie können Suchbegriffe mit und, oder und / oder nicht verknüpfen, z. B. Philo nicht logie.
Verknüpfungen können Sie mit Klammern voneinander trennen, z. B. (Philo nicht logie) oder (Psycho und logie).
Zusammenhängende Worte werden als Wortgruppe gesucht, wenn Sie sie in Anführungsstriche setzen, z. B. „Bundesrepublik Deutschland“.
Die Erweiterte Suche können Sie auch nutzen, ohne Suchbegriffe einzugeben. Sie orientiert sich dann an den Kriterien, die Sie ausgewählt haben (z. B. nach dem Land oder dem Sachgebiet).
Haben Sie in einer Kategorie kein Kriterium ausgewählt, wird die gesamte Kategorie durchsucht (z.B. alle Sachgebiete oder alle Länder).
