Mar 22, 2024
These ‘Strange Metals’ Bend the Rules of Physics
Posted by Shubham Ghosh Roy in categories: materials, quantum physics
Electrons swarm in a soup of quantum entanglement in a new class of materials called strange metals.
Electrons swarm in a soup of quantum entanglement in a new class of materials called strange metals.
The unexpected observation of an aligned spin polarization in certain twisted semiconductor bilayers calls for improved models of these systems.
If you take two overlapping tiled patterns and rotate one with respect to the other, new patterns will emerge. This motif has been used in art and architecture for millennia. Over the past 15 years, materials physicists have used a similar strategy to realize new material properties. In one implementation, two material monolayers with a hexagonal atomic lattice are overlaid with an angle between the two lattices, resulting in an additional long-range lattice structure known as a moiré pattern. In 2021, scientists observed the so-called quantum anomalous Hall (QAH) effect in such a twisted bilayer, formed of MoTe2 and WSe2 monolayers [1]. Now Zui Tao at Cornell University and colleagues have used optical spectroscopy to study the interaction between these two monolayers when they are in the QAH state [2].
Loop-shaped structures called vortex rings are remarkably stable and are seen throughout nature, appearing as bubble rings blown by dolphins and smoke rings emitted by erupting volcanoes. Recently, scientists observed vortex rings made from electron spins in magnetic materials. These structures have properties that make them attractive for use in energy-efficient data storage and processing. Now Yizhou Liu and Naoto Nagaosa at the RIKEN Center for Emergent Matter Science in Japan have proposed a way to create such magnetic vortex rings on demand [1].
Liu and Nagaosa considered a nanometer-scale cylinder made of a “chiral” magnetic material, one whose magnetic structure differs from that of its mirror image. The magnetic vortex rings that form in such a system have more diverse topologies and greater stability than those that form in other systems. In numerical simulations, the researchers injected a pulse of electric current into their chiral magnetic cylinder through a circular trench etched into the cylinder’s top surface. They then studied how the current pulse affected the material’s spin configurations.
Liu and Nagaosa observed a chain of interconnected magnetic vortex rings form along the length of the cylinder. Varying the duration and amplitude of the injected current pulse, they were able to control the topology of the vortex rings and their connections. The researchers say that the next step is for experimentalists to replicate these findings in the lab. They also suggest that their technique could be adapted to produce magnetic vortex rings in other physical systems, such as liquid crystals and Bose-Einstein condensates.
Scientists from China and Japan have identified unique features of the flow field in the lower mantle. Through their study of seismic anisotropy in the upper section of the lower mantle beneath the Philippine Sea Plate, they discovered that the ancient lower mantle flow field is still preserved there.
The study was published in Nature Geoscience.
The lower mantle is an important layer of the Earth and may play an important role in the evolution and material cycling of Earth’s interior. It is generally believed to be not only the final destination of subducted slabs, but also the birthplace of mantle plumes, which are two major styles in the evolution and material cycling of the Earth’s surface and interior. However, our knowledge of the characteristics of the flow field and geodynamics of the lower mantle is still deficient.
A team of engineers led by the University of Massachusetts Amherst and including colleagues from the Massachusetts Institute of Technology (MIT) recently announced in Nature Communications that they had successfully built a tissue-like bioelectronic mesh system integrated with an array of atom-thin graphene sensors that can simultaneously measure both the electrical signal and the physical movement of cells in lab-grown human cardiac tissue.
For the past hundred years, it has been widely recognized through X-ray and electron diffraction measurements that graphene interlayers can only accommodate a single layer of alkali metal. Each layer being fully filled by single layer alkali metal atoms is considered the theoretical charging limit.
However, there have been no reports of studies directly observing the atomic arrangement of interlayer alkali metals and verifying whether graphene layers can only accommodate a single layer of alkali metal atoms or whether other techniques can achieve higher density or multiple layers of alkali metals.
The research team developed a technique to insert dense alkali metals between graphene layers. Utilizing a high-performance low-voltage (60 kV) electron microscope, they have successfully observed the arrangement structure of alkali metal atoms between the graphene layers. The alkali metals are found densely packed in a two-layer structure in both bilayer graphene and in the surface layer graphite due to the flexible extension ability of their interlayer spacing.
A standard 3D printer and terahertz beams permit for storing data on a regular, 3D-printed piece of plastic— like cryptographic keys.
Researchers in Drexel’s College of Engineering, recently reported on the science behind a special concrete, that can warm itself up when it snows, or as temperatures approach freezing.
Chinese researchers are making variations of LK99 room temperature superconductor materials with more sulfur and copper in the chemistry. They are publishing results with stronger magnetic indications of a Meissner effect.
The chinese researchers have been online discussing their room temperature superconducting research and the challenges of the materials.