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The authors use systematic monitoring across the former USSR to investigate phenological changes across taxa. The long-term mean temperature of a site emerged as a strong predictor of phenological change, with further imprints of trophic level, event timing, site, year and biotic interactions.

Negative thermal expansion—contraction upon heating—is an unusual process that may be exploited to produce materials with zero or other controlled thermal expansion values. Azumaet al. observe negative thermal expansion in BiNiO₃which is a result of Bi/Ni charge-transfer transitions.

Attosecond pulses are useful in exploring processes involving ultrafast electron motion in atomic and molecular systems. Here the authors discuss a method to characterize the complex time-varying polarization state of broadband attosecond pulses by using asymmetry in photoelectron spectra.

The high harmonic emission that accompanies the recombination of an electron with its parent molecular ion in an intense laser field provides a snapshot of the structure and dynamics of the recombining system. Experiments on CO₂ molecules now show how to extract information from the properties of the emitted light about the underlying multi-electron dynamics with sub-Ångström spatial resolution and attosecond temporal resolution

Developing new methods for structuring light’s chirality in space would be advantageous for various next-generation applications. Here, the authors report enantio-sensitive unidirectional light bending by interacting light with isotropic chiral media.

Seven scientists share their views on some of the latest developments in attosecond science and X-ray free electron lasers (XFELs) and highlight exciting new directions.

Can the hole left by ionization in an N₂ molecule be imaged with both ångström-scale spatial and subfemtosecond temporal resolution?

Attosecond spectroscopy has been used to track the real-time motion of electrons in a krypton ion, and to probe the entanglement between an electron removed from the atom and the ion left behind.

Pressure induced charge amorphisation realised in the structurally crystalline material BiNiO₃ at low temperature, provides fundamental approaches to the study of amorphisation with charge states rather than atoms or molecules.

Understanding the physical mechanisms of photon–atom interactions on ultrafast timescales is challenging, but a new theoretical framework enables the interpretation of attoclock experiments measuring tunnelling times in hydrogen.

Sub-cycle phase-resolved attosecond interferometry is developed. The obtained phase information enables us to decouple the multiple quantum paths induced in a light-driven system, isolating their coherent contribution and retrieving their temporal evolution.

Launching electrons to the centre of an optical field with a vortex phase profile via extreme-ultraviolet photoionization makes coherent imprinting of the spatial distribution of the vortex beam onto the electron wave packet possible.

The concept of chiral topological light—a polychromatic light with chiral closed 3D polarization trajectories, space-varying with the azimuthal angle—is introduced and used for efficient sensing in chiral molecules, showcasing an example of successful application of topological concepts in optics.

Time-resolved photoelectron circular dichroism with a temporal resolution of 2.9 fs is used to track the ultrafast electron dynamics following ultraviolet excitation of neutral chiral molecules, which generate chiral currents that exhibit periodic rotation direction reversal.

We develop an optical method that can set and read the state of electrons in the valley polarization of bulk transition metal dichalcogenide semiconductors, with potential utility as digital storage at quantum coherent timescales and application in quantum computing.

Electron spin polarization is experimentally detected and investigated via strong-field ionization of xenon atoms.

A method of laser-induced recollision permits measurement with attosecond resolution of the times at which the electron leaves the tunnelling barrier and discriminates between the ionization times of two carbon dioxide orbitals.

The Berry phase is resolved in light-driven crystals, via attosecond interferometry, in which the electronic wavefunction accumulates a geometric phase as it interacts with the laser field, mapping its coherence into the emission of high-order harmonics.

Attosecond-gated interferometry is developed by combining sub-cycle temporal gating and extreme-ultraviolet interferometry. By measuring the electron’s relative phase and amplitude under a tunnelling barrier, the quantum nature of the electronic wavepacket is identified.

High-harmonic waves are generated from a MgO crystal under experimental conditions where the simple semi-classical analysis fails. High-harmonic generation spectroscopy directly probes the strong-field attosecond dynamics over multiple bands.

A single-molecule attosecond interferometry that can retrieve the spectral phase information associated with the structure of molecular orbitals, as well as the phase accumulated by an electron as it tunnels out, is demonstrated.

Here the authors show that BTLA on effector T cells interacts with HVEM on other immunosuppressive cells in the tumor microenvironment. The authors also present evidence that overcoming this checkpoint can ehance CAR T functionality.

Speed is of the essence when it comes to signal processing, but electronic switching times have reached a limit. Optically controlled tunnel currents across a nanoscale plasmonic gap could considerably accelerate future nanoelectronic devices.

Photoexcitation circular dichroism generates an ultrafast response in chiral molecules, with a much higher sensitivity than standard circular dichroism.

Freely propagating, locally and globally chiral electric fields are introduced, enabling full control over intensity, polarization and propagation direction of the nonlinear enantio-sensitive optical response of randomly oriented chiral molecules.

Detecting molecular chirality is both challenging and vital. By linking the concepts of chirality and topology, including the derivation of the Berry phase and Berry curvature in chiral molecules, the authors show that the geometrical magnetism generated by ultrafast electron currents yields an efficient set of enantiosensitive observables.

Modifications of the effective band structure of MgO crystal is investigated on a timescale within one-quarter cycle of the electromagnetic-field oscillation. The high-harmonic generation spectra show a signature of laser-induced closing of the bandgap.

Molecules that are mirror images of each other usually behave identically, unless they are interacting with other chiral objects. High-harmonic generation can provide access to the dynamics of chiral interactions on ultrafast timescales.

Light fields of energy comparable to the Coloumb field that binds valence electrons in atoms generate states where nearly free electrons oscillate in the laser field. These are now shown to exist in rare gases, acting as gain for laser filamentation.

When an electron with specific orbit — either clockwise or anticlockwise — in a rare gas atom is selectively ionized, the remaining ion will possess a stationary ring current, which can be probed in a time-delayed second ionization step.