Imagine a world where technology could reveal hidden secrets just like magic. Scientists have made a breakthrough in creating artificial optical structures called metasurfaces that can control the way they interact with polarized light. This innovation has potential applications in data encryption, biosensing, and quantum technologies.

The team from the Bionanophotonic Systems Laboratory at EPFL’s School of Engineering collaborated with researchers in Australia to create a “chiral design toolkit” that is elegantly simple yet powerful. By varying the orientation of tiny elements called meta-atoms within a 2D lattice, scientists can control the resulting metasurface’s interaction with polarized light.

The innovation was showcased by encoding two different images on a metasurface optimized for the invisible mid-infrared range of the electromagnetic spectrum. The first image of an Australian cockatoo was encoded in the size of the meta-atoms, which represented pixels, and could be decoded with unpolarized light. The second image of the Swiss Matterhorn was encoded using the orientation of the meta-atoms, so that when exposed to circularly polarized light, the metasurface revealed a picture of the iconic mountain.

“This experiment showcased our technique’s ability to produce a dual layer ‘watermark’ invisible to the human eye, paving the way for advanced anticounterfeiting, camouflage and security applications,” says Ivan Sinev, researcher at the Bionanophotonics Systems Lab.

Beyond encryption, the team’s approach has potential applications in quantum technologies, where polarized light is used to perform computations. The ability to map chiral responses across large surfaces could also streamline biosensing.

“We can use chiral metastructures like ours to sense, for example, drug composition or purity from small-volume samples. Nature is chiral, and the ability to distinguish between left- and right-handed molecules is essential, as it could make the difference between a medicine and a toxin,” says Felix Richter, researcher at the Bionanophotonic Systems Lab.

This breakthrough has opened doors to new possibilities in data encryption, biosensing, and quantum technologies. The future of technology is indeed bright, and twisted light just got a whole lot more interesting.

The discovery of a life-saving molecule whose twin is a deadly poison might seem like science fiction, but it’s a harsh reality known as “chirality.” This phenomenon occurs when two molecules have the same composition yet differ in shape and arrangement in space, much like our right and left hands. Understanding and controlling chirality is crucial for designing effective drugs.

A team from the University of Geneva (UNIGE), collaborating with the University of Pisa, has made a groundbreaking discovery in developing a new family of remarkably stable chiral molecules. This breakthrough opens up new prospects for geometry-controlled drug design and is published in the Journal of the American Chemical Society.

The concept of chirality arises when a molecule cannot be superimposed on its mirror image through any combination of rotations, translations, or geometric changes. This universal molecular asymmetry requires chemists to create chiral molecules that interact precisely with living systems.

In this context, researchers have developed a novel type of stereogenic center, where the central carbon atom is surrounded by oxygen and nitrogen atoms rather than carbon chains. This innovative design has led to the creation of stable chiral molecules whose switch from one form to its mirror sister is highly unlikely, making them suitable for safe storage without specific conditions.

The exceptional stability of these new molecular structures was demonstrated through dynamic chromatography techniques and quantum chemistry calculations. For example, it would take an estimated 84,000 years at room temperature for half a sample of the first molecule developed to transform into its mirror molecule. This remarkable stability guarantees secure storage and reduces the risk of accidental switching from a drug to an inactive or even toxic molecule.

This breakthrough in drug design and material creation has significant implications, offering new possibilities for the development of stable, controlled three-dimensional chiral molecules. As Professor Gennaro Pescitelli from the University of Pisa notes, these novel stereogenic centers provide a fresh way of organizing molecular space, opening up a whole new degree of freedom and imagination in chemical synthesis.

This discovery has far-reaching consequences for the pharmaceutical industry and material science, highlighting the importance of continued research in understanding and controlling chirality to design effective drugs and innovative materials.

The world of modern physics has been revolutionized by the emergence of twisted materials, also known as moiré structures. These remarkable systems have been hailed as today’s “alchemy” due to their ability to create entirely new phases of matter through simple geometric manipulation. By carefully controlling the twist angle, physicists can engineer entirely new quantum states, opening doors previously closed to experimental science.

One striking example of this effect is twisted bilayer graphene, where superconductivity unexpectedly emerges, even though graphene layers individually cannot become superconducting. This phenomenon has fascinated scientists and engineers alike, as it holds promise for a wide range of technological applications, from quantum simulators to ultrasensitive terahertz sensors and single-photon detectors.

However, until now, the focus has predominantly been on hexagonal lattices twisted around what are known as K-points – special points of electronic momentum symmetric under 120-degree rotations. Only a handful of materials such as graphene, MoTe2, MoSe2, and WSe2 have been explored experimentally.

In a groundbreaking new research published in Nature, an international team of researchers introduces an entirely new twisting paradigm based on the M-point of the electron momentum, significantly expanding the moiré landscape. This breakthrough has opened up a completely new class of twisted quantum materials with entirely new quantum behavior.

The position of the electronic band minimum is key,” explains Dumitru Călugăru, a Leverhulme-Peierls fellow at the University of Oxford. “By shifting our focus to the M points, we unlock a completely new class of twisted quantum materials with entirely new quantum behavior.”

The research team began by identifying hundreds of candidate materials suitable for this novel type of twisting. These materials were systematically classified based on the position of their electronic band minimum, a critical feature controlling the resulting quantum properties of the twisted layers.

Out of these materials, two (SnSe2 and ZrS2) – with band minimum at the M point — were chosen for the in-depth current study. “Unlike K-point twisting, where moiré bands typically exhibit topological characteristics, we found the M-point twisted bands to be topologically trivial yet remarkably flat,” explained Haoyu Hu, a postdoctoral researcher at Princeton.

Through extensive microscopic ab initio calculations – requiring over six months of computational effort – Yi Jiang and Hanqi Pi (Donostia International Physics Center) demonstrated that the electron bands become significantly flattened at low twist angles of about three degrees. Flattening electron bands effectively slows down electrons, enhancing their mutual interactions, and giving rise to novel quantum phenomena.

“This flattening can localize electrons in either a hexagonal lattice or a kagome lattice arrangement,” Jiang noted. Pi further elaborated, “Such localization means we can now experimentally realize diverse quantum states, potentially including quantum spin liquids.”

Quantum spin liquids, elusive states that have fascinated physicists, promise exciting applications including possible pathways to high-temperature superconductivity. However, they have never been conclusively observed experimentally in bulk materials, largely because of extreme difficulties in precisely controlling doping (adding or removing electrons) and other essential material properties.

Twisted materials, however, offer greater experimental controllability due to their tunable structure and the possibility of electrostatic gating – a technique which allows the doping of electrons without degrading the material, overcoming many of these historical hurdles.

The team’s theoretical predictions and detailed electronic models represent a major step toward observing these states in realistic materials. Other phases of matter identified, such as unidirectional spin liquids and orthonormal dimer valence bond phases, are entirely new and unique to the M-point system.

Yet, this research transcends theory. Collaborators in quantum materials chemistry – Leslie Schoop (Princeton University) and Claudia Felser (Max Planck Institute, Dresden) – have already successfully synthesized bulk crystals of several predicted candidate materials, providing the critical first step toward practical realization.

World-leading experts in 2D materials – including Dmitri Efetov (Ludwig Maximilian University of Munich), Jie Shan, and Kin Fai Mak (both at Cornell University) – then are exfoliating these bulk crystals into single-layer sheets, clearly to demonstrate the experimental feasibility of the proposed platform.

“The experimental realization of these materials is critical. Once twisted, gated, and measured, these new quantum states may become tangible realities,” said B. Andrei Bernevig, Professor of Physics at Princeton University. Every new twist we perform seems to yield surprises. Fundamentally, these materials offer a gateway to quantum states of matter nobody has envisioned.

Because they are so experimentally controllable, the possibilities truly are limitless.”