Volume 20 Issue 10, October 2024

The volume of muon beams in position–momentum space is too large to be used in a collider. A clear reduction in this volume has now been demonstrated, which brings particle physics closer to a practical muon collider for exploring the energy frontier.

The Kibble–Zurek mechanism is a key framework for describing the dynamics of continuous phase transitions. Recent experiments with ultracold gases, employing alternative methods to create a superfluid, highlight its universality.

Inducing superconductivity in quantum anomalous Hall insulators is crucial to realize topological superconductors. Now a study shows superconducting correlations in the quantum anomalous Hall state, which can convert electrons on its one-way path into holes.

A new ferroic-like phase has been discovered in highly doped superconducting cuprates. The existence of a well-defined order parameter on the supposedly disordered side of the phase diagram challenges the accepted theoretical framework.

Tuneable optical control enables the investigation of collective phases of motion in a pair of coupled levitated mechanical oscillators.

Migrating cell clusters exhibit finger-like protrusions at the front, attributed to leader cells physically dragging follower cells along. Now, an optogenetics experiment has shown that follower cells must also play a role in protrusion formation.

Understanding the mechanism of bacterial cell division is important in both fundamental and applied biology. Now, researchers have investigated the self-organization of cytoskeletal filaments and the role nematic ordering plays in cell division.

A bright, ultrashort X-ray pulse is used to transiently create and characterize warm dense copper. As the pulse intensity is increased, the opacity of copper is strongly altered. The recorded X-ray absorption spectra, substantiated by a theoretical electronic structure model, provide insight into the non-equilibrium electron dynamics during the formation of warm dense matter.

Spin-squeezed states are a resource for quantum-enhanced precision measurement. However, the theoretical foundations for scalable spin squeezing — where quantum enhancement grows with system size — have only been established for systems exhibiting all-to-all interactions. Now, by unveiling a connection to finite-temperature magnetism, scalable squeezing is extended to locally interacting systems.

Angle-resolved photoemission spectroscopy measurements identify dark electron states in palladium diselenide, cuprate superconductors, and lead halide perovskites. These dark states are attributed to the two pairs of sublattices in each of the solids, which leads to a double two-level quantum system in which double destructive interference can occur.

Many 2D or 1D materials feature fascinating collective behaviour of electrons that competes with highly localized interactions at atomic defects. By combining terahertz spectroscopy with scanning tunnelling microscopy, the ultrafast motion of these collective states can be captured with atomic spatial resolution, enabling the observation of electron dynamics at their intrinsic length and time scale.

A quantum control technique is used to directly couple trapped-ion motional modes with high fidelity, enabling non-destructive measurements of the quantum harmonic oscillator states of atomic motion. The strong coupling rate and precise manipulation of the quantum states achieved with this technique could lead to advances in quantum information processing.

High-harmonic spectroscopy on solids is an ultrafast all-optical technique to study the structure and dynamics of materials. This Review discusses areas of condensed-matter physics where this technique can provide particular insight.

Current muon beams have a phase-space volume that is too large for applications in muon colliders. Now, the reduction in the beam’s transverse emittance when passed through different absorbers in ionization cooling experiments is quantified.

Warm dense copper, created by an X-ray free-electron laser, features a transition from reverse saturable absorption to saturable absorption. The results can be used to benchmark non-equilibrium models of electronic structure in warm dense matter.

An experiment proves that strongly interacting Fermi gases driven into a superfluid phase by two different quenches display the same universal dynamics in the framework of the Kibble–Zurek mechanism.

Generating highly squeezed states for quantum sensing requires precise entanglement properties, which makes it a hard task. Now a conjecture identifies a realistic regime of magnetic order at finite temperatures that enables scalable spin squeezing.

The identification of dark states—quantum states that do not interact with photons—in real materials may help to address many unsolved issues in condensed-matter physics. Now, they have been identified in palladium diselenide.

The superconducting proximity effect has not been experimentally demonstrated in a quantum anomalous Hall insulator. Now this effect is observed in the chiral edge state of a ferromagnetic topological insulator.

The pseudogap in cuprates is often linked to superconductivity. Now bulk evidence for a pseudogap is found in doped non-superconducting Sr₂IrO₄, revealing that pseudogaps in doped Mott insulators are not necessarily a precursor to superconductivity.

The observation of phase modes of charge density wave has been a long-standing challenge. Such low-energy phase excitations have now been seen in a transition metal dichalcogenide.

Heterostructures of ferromagnets and superconductors may host exotic superconducting states. Now a circuit quantum electrodynamics technique is demonstrated that provides evidence for triplet p-wave pairing in such a heterostructure.

The Fermi liquid state in highly doped superconducting cuprates is normally thought of as disordered. Now, an observation of broken mirror symmetry in that phase suggests otherwise.

Non-reciprocal interactions between two optically levitated nanoparticles allow the observation of non-Hermitian dynamics and a mechanical lasing transition, and suggest applications in optomechanical sensing.

The tuneable and nonlinear nature of the interactions between two optically levitated nanoparticles allows the observation of the system’s non-Hermitian dynamics and a mechanical lasing transition.

A lack of non-destructive measurements and difficulty in tuning direct coupling between motional modes limits quantum information processing with trapped ions. Both features have now been achieved in an ion crystal using oscillating electric fields.

Quantum correlations are strong enough that classical users can verify that a device produces quantum entangled states using only the outcomes of local measurements. This self-testing approach has now been extended to verifying quantum measurements.

Error mitigation has helped improve the performance of current quantum computing devices. Now, a mathematical analysis of the technique suggests its benefits may not extend to larger systems.

Leader cells play an important role in guiding migratory clusters in various biological processes. Now, the mechanical organization of leader and followers within a cell cluster is shown to enable collective migration.

Treadmilling of cytoskeletal filaments is crucial for their functional self-organization. Now the mechanism underpinning this collective organization is shown to be the dissolution of misaligned filaments.

The ducts of many fluid-pumping organs feature cilia. Two structural parameters organize the different types of ducts into a continuous spectrum between ciliary carpet and flame designs depending on the fluid-pumping requirements.