International Conference on Condensed Matter Physics

  Novel magnetic memories are energy-efficient and robust. They are based on ferromagnets with operating frequencies in the gigahertz range. The operating frequency could be further increased with antiferromagnets, which, however, cannot be efficiently excited. Researchers from Kaiserslautern and Mainz have now shown that magnetic heterostructures—based on a thin antiferromagnet/ferromagnet bilayer—can combine the advantages of both material classes: A high working frequency with efficient excitation. The work has been published in the journal Physical Review Letters and has been highlighted as an Editors' suggestion. Magnetic materials play a central role in information processing and transmission in electronic devices. "We distinguish between different classes of magnets," says Professor Dr. Mathias Weiler, who heads the Applied Spin Phenomena group of the Department of Physics at the University Kaiserslautern-Landau. "The ferromagnets have a net magnetization and ...

  Icy planets, such as Uranus (U) and Neptune (N), are found in both our solar system and other solar systems across the universe. Nonetheless, these planets, characterized by a thick atmosphere and a mantle made of volatile materials (e.g., hydrogen water, ammonia, etc.), are the least explored class of planets; thus so far little is known about their origin, interior structure and composition. The Voyager probes, two robotic systems launched by NASA on a quest to explore the outer solar system, recorded interesting measurements suggesting that icy planets have peculiar magnetic fields. These measurements showed that unlike other types of planets, such as terrestrial planets and gas giants, icy planets do not have a dipolar magnetic field, and are thus without clear North and South magnetic poles. Researchers at Ecole Polytechnique, Sorbonne Université and other institutes in Europe recently carried out a study aimed at better understanding under which form matter could exist insi...

  Superconductors — materials that conduct electricity without resistance — are remarkable. They provide a macroscopic glimpse into quantum phenomena, which are usually observable only at the atomic level. Beyond their physical peculiarity, superconductors are also useful. They’re found in medical imaging, quantum computers, and cameras used with telescopes. But superconducting devices can be finicky. Often, they’re expensive to manufacture and prone to err from environmental noise. That could change, thanks to research from Karl Berggren’s group in the Department of Electrical Engineering and Computer Science. The researchers are developing a superconducting nanowire, which could enable more efficient superconducting electronics. The nanowire’s potential benefits derive from its simplicity, says Berggren. “At the end of the day, it’s just a wire.” Berggren will present a summary of the research at this month’s IEEE Solid-state Circuits Conference. Resistance is futile Most metals ...

  Scientists from the University of Ottawa and the Max Planck Institute for the Science of Light are proposing a breakthrough approach that will facilitate discoveries in materials science by combining terahertz (THz) spectroscopy and real-time monitoring. Terahertz waves are electromagnetic waves that can reveal hidden secrets of matter. They can capture fast changes in materials invisible to other types of radiation. Scientists can now use terahertz waves to record real-time movies of hot electrons in silicon at 50,000 frames per second—faster than ever before. Led by Jean-Michel Ménard, associate professor of physics at the University of Ottawa's Faculty of Science, a team of scientists used two techniques, chirped-pulse encoding and photonic time-stretch. The study, "Single-pulse terahertz spectroscopy monitoring sub-millisecond time dynamics at a rate of 50 kHz," was published in Nature Communications. The first technique imprints the information carried by a THz pul...

  A new study determines the thermal properties of advanced solid materials, based on first-principles calculations of quantum vibrations. As the energy demands of our modern world continue to grow, there is a crucial need to understand how heat flows through the materials we use to build our technology. Through new research published in The European Physical Journal B, Vinod Solet and Sudhir Pandey at the Indian Institute of Technology Mandi have accurately estimated the thermal properties of a particularly promising alloy, based on first-principles calculations of phonons. Composed of scandium (Sc), silver (Ag), and carbon (C), this alloy could soon become a key component of devices which convert heat into electricity, while its low reflectivity and strong photon absorption would make it especially well-suited for highly efficient solar cells. Phonons are quantum particles which represent the smallest units of vibrational energy in a solid, or 'quantum' of heat in other words...

  Skyrmions are microscopic magnetic vortices that can form in certain materials. First detected in 2009, they are of interest to researchers because they could be harnessed for new forms of data storage. As theoreticians predicted, there are also so-called antiskyrmions, which were discovered 10 years after skyrmions Researchers from HZDR, MPI CPfS, IFW Dresden, and the University of South Florida have now used an ion beam saw and sophisticated measurement techniques to get to the bottom of this complex phenomenon, which they report on in the journal Communications Materials. "In a sense, an antiskyrmion is the antiparticle of the skyrmion. Both are called quasiparticles, which owe their properties to the collective interaction of a large number of particles in solid matter. Their properties differ greatly from those of their underlying elementary particles," says Dr. Toni Helm of the Dresden High Magnetic Field Laboratory (HLD) at HZDR. Helm uses a metaphor to illustrate th...

Laboratory experiments elucidate the directions and speeds at which acoustic waves propagate in the type of iron that likely makes up Earth’s core. By compressing a specific crystalline orientation of iron in a diamond-anvil cell, researchers have for the first time created a version of the metal in the structure that it likely takes in Earth’s core. By exploring uncharted pathways within the pressure–temperature phase space, scientists have achieved a groundbreaking milestone: the synthesis of single-crystalline iron in the structure that it likely assumes in Earth’s core . This accomplishment allows for precise measurements of the elastic properties of iron in various crystalline directions. Additionally, the study helps to identify a theoretical approach that could uncover the underlying mechanisms responsible for the observed anisotropy in seismic-wave propagation throughout Earth. By elucidating the properties of iron in its core structure, this research takes us one step closer ...

  Scientists at Stockholm University have discovered that water can exhibit a similar behavior to that of a liquid crystal when illuminated with laser light. This effect originates by the alignment of water molecules, which exhibit a mixture of low- and high-density domains that are more or less prone to alignment. The results, reported in Physics Review Letters, are based on a combination of experimental studies using X-ray lasers and molecular simulations.Liquid crystals were considered a mere scientific curiosity when they were first discovered in 1888. Over 100 years later, they are one of the most widely used technologies, present in digital displays (LCDs) of watches, TVs and computer screens. Liquid crystals work by applying an electric field, which makes the neighboring molecules of a liquid align, in a way that resembles a crystal. Water too can be distorted towards a liquid crystal, when illuminated with laser light.  It is known that the electric field of the laser ...

Superconductors are promising for various applications, ranging from magnets to generators and transformers. However, the performance of these materials decreases dramatically in high magnetic fields. Magnetic flux quanta, i.e. vortices, appear in a superconducting film upon applying a magnetic field. These vortices move throughout the superconductor under the influence of a Lorentz force, causing thermal dissipation and a reduction in JC. Vortices can be immobilized, or pinned, by the introduction of non-superconducting defects of the size of their core, i.e. a few nm. These so called artificial pinning centers (APCs) should effectively decrease the magnetic field dependence of JC. The production of such a superconducting coating comprises a number of steps which we focus on in our research group: (1) Synthesis of metal oxide nanocrystals, using either classical hot-injection surfactant-assisted synthesis or microwave-assisted surfactant-free solvothermal synthesis. Both methods are...

Superconductivity is associated with magnetic flux expulsion, which in turn causes magnetic levitation in the above demonstration (see video). J. Robert Schrieffer was the co-recipient of the Nobel Prize for developing the BCS theory of superconductivity. Three decades ago, defying many expectations, new forms of quantum matter were discovered including unconventional superconductors and quantum Hall states. We now understand that just like a large collection of atoms can organize itself into solid, liquid or gas phase, quantum matter can organize itself into "valence bond solid", "spin liquid" and "Fermi gas" phases among many others. The quest to understand such phases and the conditions under which they occur has spawned the study of correlated systems. These include, but are not restricted to, moire systems (e.g. "twisted graphene"), quantum magnets, quantum Hall states, topological matter, metal-insulator transitions and more. Our group mai...

  A team from Ames National Laboratory conducted an in-depth investigation of the magnetism of TbMn6Sn6, a Kagome layered topological magnet. They were surprised to find that the magnetic spin reorientation in TbMn6Sn6 occurs by generating increasing numbers of magnetically isotropic ions as the temperature increases. Rob McQueeney, a scientist at Ames Lab and project lead, explained that TbMn6Sn6has two different magnetic ions in the material, terbium and manganese. The direction of the manganese moments controls the topological state, "But it's the terbium moment that determines the direction that the manganese points," he said. "The idea is, you have these two magnetic species and it is the combination of their interactions which controls the direction of the moment." In this layered material, there is a magnetic phase transition that occurs as the temperature increases. During this phase transition, the magnetic moments switch from pointing perpendicular to ...

  Scientists from the Department of Energy's Ames National Laboratory made an intriguing discovery while conducting experiments to characterize magnetism in a material known as a dilute magnetic topological insulator where magnetic defects are introduced. Despite this material's ferromagnetism, the team discovered strong antiferromagnetic interactions between some pairs of magnetic defects that play a key role in several families of magnetic topological insulators. Topological insulators (TIs) as their name indicates, are insulators. However, because of their unique electronic band structure, they conduct electricity on the surface under the right conditions. By introducing magnetism, TIs can transmit electrical currents from one point to another without any heat generation or energy loss. This quality means that they have the potential to reduce future energy footprints for computing and electricity transmission. According to Rob McQueeney, a scientist from Ames Lab and a memb...

  A physicist at the University of Waterloo is among a team of scientists who have described how glasses form at the molecular level and provided a possible solution to a problem that has stumped scientists for decades. Their simple theory is expected to open up the study of glasses to non-experts and undergraduates as well as inspire breakthroughs in novel nanomaterials. The paper published by physicists from the University of Waterloo, McMaster University, ESPCI ParisTech and Université Paris Diderot appeared in the prestigious peer-reviewed journal, Proceedings of the National Academy of Sciences (PNAS). Glasses are much more than silicon-based materials in bottles and windows. In fact, any solid without an ordered, crystalline structure—metal, plastic, a polymer—that forms a molten liquid when heated above a certain temperature is a glass. Glasses are an essential material in technology, pharmaceuticals, housing, renewable energy and increasingly nano electronics. "We were sur...