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Category: particle physics – Page 15

New model explains plutonium’s peculiar behavior

Normally, materials expand when heated. Higher temperatures cause atoms to vibrate, bounce around and take up a larger volume. However, for one specific phase of plutonium—called delta-plutonium—the opposite inexplicably occurs: it shrinks above room temperature.

As part of its national security mission, Lawrence Livermore National Laboratory (LLNL) aims to predict the behavior of plutonium in all of its phases. Unraveling the mystery behind delta-plutonium’s abnormal behavior at high temperatures is an important piece of the picture.

In a new study, published in Reports on Progress in Physics, researchers from LLNL demonstrate a model that can reproduce and explain delta-plutonium’s thermal behavior and unusual properties. The model calculates the material’s free energy, a quantity that reflects the amount of available or useful energy in a system.

Researchers discover universal rules of quantum entanglement across all dimensions

A team of theoretical researchers used thermal effective theory to demonstrate that quantum entanglement follows universal rules across all dimensions. Their study was published online in Physical Review Letters.

“This study is the first example of applying thermal effective theory to quantum information. The results of this study demonstrate the usefulness of this approach, and we hope to further develop this approach to gain a deeper understanding of quantum structures,” said lead author and Kyushu University Institute for Advanced Study Associate Professor Yuya Kusuki.

In , two particles that are far apart behave independently. However, in , two particles can exhibit strong correlations regardless of the distance between them. This quantum correlation is known as quantum entanglement.

Ghost particles may secretly decide the fate of collapsing stars

Neutrinos are cosmic tricksters, paradoxically hardly there but lethal to stars significantly more massive than the sun. These elementary particles come in three known “flavors”: electron, muon and tau. Whatever the flavor, neutrinos are notoriously slippery, and much about their properties remains mysterious. It is almost impossible to collide neutrinos with each other in the lab, so it is not known if neutrinos interact with each other according to the standard model of particle physics, or if there are much-speculated “secret” interactions only among neutrinos.

Now a team of researchers from the Network for Neutrinos, Nuclear Astrophysics, and Symmetries (N3AS), including several from UC San Diego, have shown, through theoretical calculations, how collapsing massive stars can act as a “neutrino collider.” Neutrinos steal thermal energy from these stars, forcing them to contract and causing their electrons to move near light speed. This drives the stars to instability and collapse.

Eventually the collapsing star’s density becomes so high that the neutrinos are trapped and collide with each other. With purely standard model interactions, the neutrinos will be mostly electron flavor, the matter will be relatively “cold,” and the collapse will likely leave a neutron star remnant. However, secret interactions that change neutrino flavor radically alter this scenario, producing neutrinos of all flavors and leading to a mostly neutron “hot” core that may lead to a black hole remnant.

‘Neglected’ particles that could rescue quantum computing

One of the most promising approaches to overcoming this challenge is topological quantum computing, which aims to protect quantum information by encoding it in the geometric properties of exotic particles called anyons. These particles, predicted to exist in certain two-dimensional materials, are expected to be far more resistant to noise and interference than conventional qubits.

“Among the leading candidates for building such a computer are Ising anyons, which are already being intensely investigated in condensed matter labs due to their potential realization in exotic systems like the fractional quantum Hall state and topological superconductors,” said Aaron Lauda, professor of mathematics, physics and astronomy at the USC Dornsife College of Letters, Arts and Sciences and the study’s senior author. “On their own, Ising anyons can’t perform all the operations needed for a general-purpose quantum computer. The computations they support rely on ‘braiding,’ physically moving anyons around one another to carry out quantum logic. For Ising anyons, this braiding only enables a limited set of operations known as Clifford gates, which fall short of the full power required for universal quantum computing.”

But in a new study published in Nature Communications, a team of mathematicians and physicists led by USC researchers has demonstrated a surprising workaround. By adding a single new type of anyon, which was previously discarded in traditional approaches to topological quantum computation, the team shows that Ising anyons can be made universal, capable of performing any quantum computation through braiding alone. The team dubbed these rescued particles “neglectons,” a name that reflects both their overlooked status and their newfound importance. This new anyon emerges naturally from a broader mathematical framework and provides exactly the missing ingredient needed to complete the computational toolkit.

Research examines how ripples affect nanoscopic materials

When materials are created on a nanometer scale — just a handful of atoms thick — even the thermal energy present at room temperature can cause structural ripples. How these ripples affect the mechanical properties of these thin materials can limit their use in electronics and other key systems.

New research validates theoretical models about how elasticity is scale-dependent — in other words, the elastic properties of a material are not constant, but vary with the size of the piece of material.

Assistant Professor Jian Zhou, PhD ’18, collaborated with researchers from Argonne National Laboratory, Harvard University, Princeton University and Penn State University for a recently published paper in the Proceedings of the National Academy of Sciences.

Using a semiconductor manufacturing process, the team created alumina structures 28 nanometers thick (more than 1,000 times thinner than the diameter of a human hair) on the silicon wafer with thermal-like static ripples, then tested them with lasers to measure their behavior. To remove possible stress to the material that could affect the results, cantilevers held the wafers during testing.

Understanding how thin materials behave is key to electronics and other technology.

Heavy fermions entangled: Discovery of Planckian time limit opens doors to novel quantum technologies

A joint research team from Japan has observed “heavy fermions,” electrons with dramatically enhanced mass, exhibiting quantum entanglement governed by the Planckian time—the fundamental unit of time in quantum mechanics. This discovery opens up exciting possibilities for harnessing this phenomenon in solid-state materials to develop a new type of quantum computer. The findings are published in npj Quantum Materials.

Heavy fermions arise when conduction electrons in a solid interact strongly with localized magnetic electrons, effectively increasing their mass. This phenomenon leads to unusual properties like unconventional superconductivity and is a central theme in condensed matter physics. Cerium-rhodium-tin (CeRhSn), the material studied in this research, belongs to a class of heavy fermion systems with a quasi-kagome lattice structure, known for its geometrical frustration effects.

Researchers investigated the electronic state of CeRhSn, known for exhibiting non-Fermi liquid behavior at relatively high temperatures. Precise measurements of CeRhSn’s reflectance spectra revealed non-Fermi liquid behavior persisting up to near room temperature, with heavy electron lifetimes approaching the Planckian limit. The observed spectral behavior, describable by a single function, strongly indicates that heavy electrons in CeRhSn are quantum entangled.

Experiment Recreates The Universe’s Very First Chemical Reactions

The first chemical reactions in the wake of the Big Bang have been recreated for the first time in conditions similar to those in the baby Universe.

A team of physicists led by Florian Grussie of the Max Planck Institute for Nuclear Physics (MPIK) in Germany has reproduced the reactions of the helium hydride ion (HeH+), a molecule made from a neutral helium atom fusing with an ionized atom of hydrogen.

These are the first steps that lead to the formation of molecular hydrogen (H2), the most abundant molecule in the Universe and the stuff from which stars are born. The new work, therefore, elucidates some of the earliest processes that gave rise to the Universe as we know it today.

Dark Mirror of Our Own Universe Could Explain Quirks in Gravity

Since conventional explanations have failed to pony up dark matter, one physicist is looking towards the unconventional.

In a series of two papers, physicist Stefano Profumo of the University of California, Santa Cruz has proposed two strange, but not impossible, origins for the mystery material responsible for the excess gravitational effects we see out there in the Universe.

In the first, published in May 2025, he proposes that dark matter could have been born in a dark matter ‘mirror’ of our own Universe, where matter is made of dark versions of particles akin to our protons and neutrons.

New Technique Sheds Light on Chemistry at the Bottom of the Periodic Table

The periodic table is one of the triumphs of science. Even before certain elements had been discovered, this chart could successfully predict their masses, densities, how they would link up with other elements, and a host of other properties.

But at the bottom of the periodic table, where massive atoms are practically bursting at the seams with protons, its predictive power might start to break down. Experiments to study the chemistry of the heaviest elements — especially the superheavy elements, which have more than 103 protons — have long been a challenge. Despite using specialized facilities, researchers have been unable to definitively identify the molecular species they produce in experiments. This uncertainty has hindered progress in the field, since scientists have had to rely on educated guesses rather than precise knowledge of the chemistry being observed.

Now, researchers have used the 88-Inch Cyclotron at the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) to develop a new technique to make and directly detect molecules containing heavy and superheavy elements. In a study published today in the journal Nature, a team of researchers from Berkeley Lab, UC Berkeley, and The University of Alabama used the method to create molecules containing nobelium, element 102. It is the first time scientists have directly measured a molecule containing an element greater than 99.

Scientists create gold hydride by combining gold and hydrogen under extreme conditions

Serendipitously and for the first time, an international research team led by scientists at the U.S. Department of Energy’s SLAC National Accelerator Laboratory formed solid binary gold hydride, a compound made exclusively of gold and hydrogen atoms.

The researchers were studying how long it takes hydrocarbons, compounds made of carbon and hydrogen, to form diamonds under extremely high pressure and heat.

In their experiments at the European XFEL (X-ray Free-Electron Laser) in Germany, the team studied the effect of those extreme conditions in hydrocarbon samples with an embedded gold foil, which was meant to absorb the X-rays and heat the weakly absorbing hydrocarbons. To their surprise, they not only saw the formation of diamonds, but also discovered the formation of gold .

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