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.”

Atacamite, a vibrant emerald-green mineral found in the Atacama Desert in Chile, has been discovered to possess a rare property that defies conventional physics. The mineral exhibits magnetocaloric behavior at low temperatures, meaning its temperature changes significantly when subjected to a magnetic field. A team of researchers from TU Braunschweig and the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) has been investigating this phenomenon, and their findings could lead to the development of new materials for energy-efficient magnetic cooling.

The researchers found that atacamite’s unique geometric structure, consisting of long chains of small, linked triangles known as sawtooth chains, is responsible for its magnetocaloric behavior. This arrangement creates “magnetic frustration,” where the spins in the copper ions cannot align themselves antiparallel to one another due to the triangular structure. As a result, the spins only arrange themselves at very low temperatures (under 9 Kelvin) in a static alternating structure.

When the researchers applied an extremely high magnetic field to the atacamite crystal, something surprising occurred: the material exhibited a significant cooling effect, with its temperature dropping to almost half of its original value. This strong magnetocaloric effect has fascinated the researchers, as it is unusual for magnetically frustrated materials to exhibit such behavior.

Further studies using magnetic resonance spectroscopy have revealed that the magnetic order in atacamite is destroyed when a magnetic field is applied. This destruction of magnetic order explains why the material’s temperature changes significantly in response to the magnetic field. The team has also conducted complex numerical simulations, which have provided an explanation for the mineral’s unexpected behavior: the magnetic moments on the tips of the sawtooth chains mediate a weak coupling to neighboring chains, leading to the removal of long-range magnetic order.

The researchers believe that their work could inspire further research into innovative magnetocaloric materials within the class of magnetically frustrated systems. While atacamite itself is unlikely to be mined for use in cooling systems, its unique properties provide valuable insights into the fundamental mechanisms governing magnetic behavior in solids. The discovery of this rare property could potentially lead to breakthroughs in energy-efficient magnetic cooling technologies, revolutionizing the way we think about and use refrigeration.

The field of catalysis has revolutionized industries and everyday life, with around 80% of all chemical products relying on this principle. One particularly effective catalyst is platinum, but its rarity and expense make it essential to use it efficiently. Researchers at ETH Zurich have made a groundbreaking discovery by mapping the atomic environments of single platinum atoms in solid supports, paving the way for optimized production of single-atom catalysts.

Using nuclear magnetic resonance (NMR), a team led by Javier Pérez-Ramírez and Christophe Copéret was able to study the individual platinum atoms in detail. This method, typically used for investigating molecules, allowed them to show that the atomic environments of these atoms can have very different properties, influencing their catalytic action.

The researchers found that each platinum atom has a unique combination of neighboring atoms and spatial orientation, similar to the distinct tones in an orchestra. By developing a computer code with the help of a simulation expert, they were able to filter out the different “tones” and create a map of the atomic environments surrounding the platinum atoms.

This breakthrough enables the optimization of production protocols for single-atom catalysts, where all platinum atoms can have tailored environments. The researchers aim to develop more efficient catalytic materials, which is crucial for a greener future in industries such as fuel cells and exhaust catalysts.

The discovery has significant intellectual property implications, allowing the precise description of catalysts at the atomic level and enabling patent protection. This innovation has far-reaching consequences for the development of more sustainable technologies and could transform the field of catalysis forever.