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Spin Supercurrents in Superconducting Altermagnets

Materials from a new class of magnets could host permanent dissipationless spin currents when they enter a superconducting state.

Superconductors are famous for transporting electric charge with zero resistance. This ability underpins technologies such as MRI scanners, quantum computers, and sensitive magnetometers known as superconducting quantum interference devices. However, in the field of spintronics—which seeks to process information using electron spin rather than charge—achieving a similar long-range dissipationless transport has remained elusive. In ordinary metals, electron spins are highly susceptible to scattering and spin-orbit coupling, both of which cause spin currents to decay over short distances. Although research in superconducting spintronics based on ferromagnets has made progress [1, 2], ferromagnets produce stray magnetic fields that interfere with external circuit elements, and their internal magnetic fields tend to destroy superconductivity.

Ryugu asteroid samples contain all DNA and RNA building blocks, bolstering origin-of-life theories

All the essential ingredients to make the DNA and RNA underpinning life on Earth have been discovered in samples collected from the asteroid Ryugu, scientists said Monday.

The discovery comes after these building blocks of life were detected on another asteroid called Bennu, suggesting they are abundant throughout the solar system.

One longstanding theory is that life first began on Earth when asteroids carrying fundamental elements crashed into our planet long ago.

Next-gen interferometric diffusing wave spectroscopy achieves 20x signal boost in cerebral blood flow monitoring

Cerebral blood flow is essential for normal brain function and often perturbed in neurological disease. If one shines a source of coherent light on perfused tissue, the detected speckles, or “grains” of light fluctuate, or “dance,” at a rate proportional to blood flow in the volume sampled by the light. In brain tissue, this concept can be harnessed to measure the cerebral blood flow index (CBFi).

However, to date, implementations of this principle for noninvasive adult human brain monitoring—collectively known as diffuse correlation spectroscopy (DCS)—have achieved limited brain sensitivity. This is because the brain is 1–2 centimeters deep beneath the scalp and skull, meaning that the light must sample the superficial tissue before reaching the brain.

While the collection points can be moved further from the source to address this issue by improving sampling of the brain, this strategy requires many photon-counting channels to detect highly attenuated light far from the source. DCS becomes prohibitively expensive as the number of channels increases.

A clear roadmap for engineering combs of light

Optical frequency combs—laser sources that emit evenly spaced colors of light—are foundational, ubiquitous tools for precision measurement, found in optical clocks, gas-sensing spectrometers, and instruments that detect the light signatures of exoplanets. Traditionally, frequency combs are produced by large, fiber-laser systems ranging from the size of a shoebox to a refrigerator.

Engineers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) are at the forefront of shrinking these powerful laser sources onto photonic chips to make “microcombs” at millimeter to micron scales, useful not only for their smaller size, but in next-generation telecommunications applications, such as generating multiple data carriers over a single optical fiber.

New research led by Marko Lončar, the Tiantsai Lin Professor of Electrical Engineering and Applied Physics, describes a new, generalized model for how to design so-called resonant electro-optic microcombs on thin-film lithium niobate, a material featuring a strong electro-optic effect, or the ability to efficiently mix electronic signals with optical ones.

Laser-assisted electron scattering seen with circularly polarized light for the first time

Researchers from Tokyo Metropolitan University have succeeded in detecting laser-assisted electron scattering (LAES) using circularly polarized light for the first time. The use of circularly polarized light promises valuable insights into how atomic scale “helicity” impacts how electrons interact with matter and light.

Using synchronized femtosecond laser pulses and electron pulses directed at argon atoms, they succeeded in detecting a LAES signal showing excellent agreement with theory. The findings are published in The Journal of Chemical Physics.

LAES is a cutting-edge tool for understanding how electrons interact with matter under the influence of strong fields. When electrons are fired at atoms or molecules, they are scattered in all directions; the presence of strong light can change the way in which the scattering takes place due to an exchange of energy with the surrounding light field.

Not just spin—electron orbitals can provide new method for controlling magnetism

Research is actively underway to develop a “dream memory” that can reduce heat generation in smartphones and laptops while delivering faster performance and lower power consumption. Korean researchers propose a new possibility for controlling magnetism using the exchange interaction of electron orbitals—the motion of electrons orbiting around an atomic nucleus—rather than relying on the conventional exchange interaction of electron spin, the rotational property of electrons inside semiconductors.

A joint research team led by Professor Kyung-Jin Lee of the Department of Physics at KAIST and Professor Kyoung-Whan Kim of the Department of Physics at Yonsei University has established, for the first time in the world, a new theoretical framework enabling magnetism to be freely controlled through orbital exchange interaction, surpassing the limitations of conventional technologies that control magnetism using electric currents. The study is published in the journal Nature Communications.

Until now, next-generation memory research has mainly focused on the spin of electrons. Spin refers to the property of electrons that rotate on their own axis like tiny spinning tops, and information can be stored by using the direction of this rotation. However, electrons simultaneously move around the atomic nucleus along paths known as orbitals.

Could a recently detected ultra-high-energy neutrino be linked to new physics?

Neutrinos are extremely lightweight and electrically neutral particles that rarely interact with ordinary matter. Due to these rare interactions, neutrinos can travel across space almost entirely unaffected, carrying information about highly energetic cosmological events, such as exploding stars or supermassive black holes.

The KM3NeT neutrino telescope, an observatory located at the bottom of the Mediterranean Sea, recently detected the presence of a neutrino carrying extremely high energy, above 100 PeV (peta-electronvolts). This is one of the most energetic neutrinos observed to date.

Theoretical predictions suggested that another large-scale neutrino detector, namely the IceCube detector, would also observe similar high-energy neutrino events. However, this did not happen, which might potentially hint at some new physics, such as a new type of neutrinos or non-standard interactions, that are not included in the standard model of physics.

Physicists break longstanding high-temperature superconductivity record at ambient pressure

Researchers from the Texas Center for Superconductivity (TcSUH) and the department of physics at the University of Houston have broken the temperature record for superconductivity at ambient pressure—a breakthrough that could eventually lead to more efficient ways to generate, transmit, and store energy.

The UH team achieved a transition temperature (Tc) of 151 Kelvin (about minus 122 degrees Celsius) under ambient pressure—the highest ever recorded for all the reported superconductors at ambient pressure since the discovery of superconductivity in 1911. The transition temperature is the point below which a material becomes superconducting, meaning electricity can flow through it without resistance.

Raising this temperature has been a major goal in superconductivity research for decades. The closer scientists can push the Tc toward room temperature, the more practical and affordable superconducting technologies could become.

New microscope offers sharper view into momentum space

Electrons are tiny and constantly in motion. How they behave in a crystal lattice determines key material properties: electrical conductivity, magnetism, or novel quantum effects. Anyone aiming to develop the information technologies of tomorrow must understand what electrons do. At Forschungszentrum Jülich, a new tool is now available for this purpose: a momentum microscope that was fully developed and built on site. “Internationally, we are currently seeing rapidly growing interest in this method,” explains Dr. Christian Tusche from Forschungszentrum Jülich.

Dr. Christian Tusche already played a key role in advancing momentum microscopy during his time at the Max Planck Institute of Microstructure Physics in Halle. Since moving to Jülich in 2015, he has continued to drive its development forward. His work has been recognized with several awards, including the Kai Siegbahn Prize in 2018 and the Innovation Award on Synchrotron Radiation in 2016. Most recently, he published a review article on the method in the journal Applied Physics Letters.

In recent years, numerous instruments have been commissioned at synchrotron facilities and X-ray lasers around the world. “The new device we built together with the Mechanical Workshop is a real innovation. There is currently nothing like it available from any specialist company,” says Dr. Tusche.

Globular cluster NGC 5824 is embedded in a dark matter halo, study suggests

Using data from the Magellan Clay telescope and the Canada-France-Hawaii Telescope (CFHT), astronomers have investigated a galactic globular cluster known as NGC 5824. Results of the new study, available in a paper published March 5 on the arXiv pre-print server, suggest that the cluster is embedded in a dark matter halo.

NGC 5,824 is an old globular cluster (GC) located some 104,000 light years away in the Milky Way’s outer halo. It has a mass of about 1 million solar masses, an age of 12.8 billion years and is the second brightest globular cluster of the outer halo clusters. NGC 5,824 is known to have a diffuse stellar envelope that extends beyond its tidal radius and symmetrically surrounds the cluster.

Given that the origin of the stars in this envelope and whether they remain gravitationally bound to the cluster center is still unclear, a team of astronomers led by Paula B. Díaz of the University of Chile decided to investigate NGC 5,824 by analyzing the data from the survey of the Milky Way outer halo satellites, based on the images acquired by CFHT and the Magellan Clay telescope. The study was complemented by data from ESA’s Gaia satellite.

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