Improved measurements of an electronic transition in helium-4 atoms constrain the size difference between helium-4 and helium-3 nuclei.
Category: particle physics
Hidden electric space waves are quietly cleaning Earth’s ‘killer’ electrons
High above our heads, a silent battle is unfolding within Earth’s magnetic shield. For decades, scientists have tracked “killer electrons”—ultrafast particles capable of piercing satellite armor and endangering astronauts as they zip through the Van Allen radiation belts. While we knew these dangerous particles eventually leak out of the belts and into the atmosphere, the primary mechanism “cleaning” the highest-energy electrons has remained a persistent mystery of space weather.
Now, a study published in Geophysical Research Letters has uncovered the culprit by diving into three years of NASA’s Van Allen Probes data. Led by Lixian Yang and a team of researchers, the study identifies a hidden population of chorus waves that defies standard physics models.
Unlike typical space waves that are mostly magnetic, these highly oblique quasi-electrostatic (HOQE) waves possess an electric field so powerful it dominates their character. This unique electric punch allows them to knock electrons with energies up to 2 MeV out of orbit and into the atmosphere, scattering them with a force far more potent than any previous model predicted.
Out-of-equilibrium cesium atoms reveal fractional Fermi seas, exposing new critical quantum phase
In a new study published in Physical Review Letters, a team from the Nägerl group, together with theory collaborator Alvise Bastianello from the CNRS and the Université Paris-Dauphine, demonstrates that highly unusual quantum states known as “fractional Fermi seas” can be quantum engineered.
By driving quantum particles—here, ultracold cesium atoms under one-dimensional confinement—far out of equilibrium through cyclic changes of the particle interaction, a novel critical phase of matter emerges, going beyond what is known from the celebrated Tomonaga-Luttinger liquid theory. The new publication serves as the theoretical companion to, and foundation for, recent experimental work in the group of Hanns-Christoph Nägerl at the Department of Experimental Physics.
Usually, particles in the quantum world follow strict rules about how they organize themselves at low temperatures. As Bastianello explains, “Fermions, for instance, stack neatly into the available energy states to form the so-called ‘Fermi sea.’ But what happens if one forces interacting atoms to continuously cycle through extreme conditions, smoothly shifting them from strongly repelling each other to strongly attracting each other?”
Diamond-based particle detector captures one-picosecond electron bursts for high-rate beam diagnostics
Physicists at UC Santa Cruz and other institutes across California and New Mexico have developed a detection system that will allow next-generation particle accelerators to better reveal fundamental biological and chemical processes, as well as advance critical areas such as materials science and energy research.
The Advanced Accelerator Diagnostics Collaboration, a group of two University of California campuses and three U.S. national laboratories, came together to solve a growing need for high-rate beam diagnostics. These accelerators will now jump from 120 pulses a second to 1 million pulses a second, straining current beam diagnostic systems. The results are now published in the journal Physical Review Accelerators and Beams.
“It really highlights the power of collaboration between universities and national laboratories,” said Bruce Schumm, the Long Family Professor of Experimental Physics. “If you took away Lawrence Berkeley Lab, if you took away Los Alamos, if you took away UC Davis, any of those, the whole thing would have fallen apart.”
How do flocking birds and schools of fish move? New research offers crystal-clear answer
Flocking birds and schools of fish are a familiar sight. While previous research has uncovered the broad dynamics driving these movements, their underlying intricacies remain a mystery. Now a study by a team of New York University mathematicians offers new insights into these phenomena. It reveals that flocks and schools behave in ways similar to a soft crystalline material, with individual birds and fish serving as “atoms” that are evenly spaced in a lattice-like formation.
The findings, reported in the journal Physical Review Fluids, offer detailed insights into the hydrodynamic and aerodynamic interactions crucial in aerospace and automotive engineering, robotics and energy harvesting.
“Our findings offer a new way to understand how animal collectives coordinate movement and respond to their environment,” says Christiana Mavroyiakoumou, a researcher at NYU’s Courant Institute School of Mathematics, Computing, and Data Science at the time of the study and now a fellow at Oxford University’s Mathematical Institute. “More specifically, lines of birds or fish behave like an elastic material with regularly spaced individuals held together by flexible, or spring-like, bonds—akin to soft crystalline substances in which atoms are arranged in an orderly, repeating pattern.”
Electrically tunable spin polarization in graphene opens path toward low-power spintronic devices
Researchers at the National Graphene Institute, in collaboration with the National University of Singapore, have shown that the magnetic behavior of electrons in graphene can be precisely controlled using electricity, revealing unusually large spin signals in a carefully engineered graphene system.
The study, published in Nature Communications, demonstrates how placing graphene close to a magnetic material can influence the spin of electrons without permanently altering graphene itself. By combining this magnetic proximity effect with graphene superlattices and operating at very low charge densities, the researchers were able to strongly tune how spins move through the material.
“This work shows that by combining graphene with nearby magnetic materials, we can gain a high level of control over electron spin using electrical signals alone,” said Dr. Daniel Burrow, from the University of Manchester. “In simple terms, we are learning how to pass information through graphene using the spin of electrons rather than their electrical charge.”
Reversible chirality switching in MoS₂ generates spin currents without magnets
A newly developed method allows researchers to dynamically switch chirality—a particular lack of mirror symmetry—to generate spin currents in semiconductors, researchers from Science Tokyo report. Their approach relies on the reversible insertion and removal of small chiral molecules from the interlayer gaps of a layered, nonchiral semiconductor material using electrochemistry.
The findings could pave the way for the development of novel chiral spintronic materials and technologies that do not rely on magnets or magnetic fields.
AI-driven optical tweezers sort hundreds of particles per hour without humans
Just as self-driving cars navigate traffic without a human behind the wheel, laboratory instruments are now being developed that can design, carry out and repeat experiments independently, 24 hours a day.
Researchers at the University of Gothenburg and other institutions have now developed an AI system capable of speeding up the operation of optical tweezers, dubbed SmartTrap. The work has been published in Nature Methods.