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When free electrons emit light, an entangled electron–photon state is created. Here measurements of the correlated multiparticle system have been used to produce non-classical photonic states.

The authors report the emergence of a transient hexatic state during laser-induced transformation between two charge-density wave (CDW) phases in a thin film of the CDW material 1T-TaS₂.

The thermalization of acoustic phonons after photoexcitation is traced by electron pulses in TiSe₂, and the excitonic contribution to the structural order parameter of the material’s charge density wave phase is quantified.

Free-electron homodyne detection allows measuring phase-resolved optical responses in electron microscopy, demonstrated in the imaging of plasmonic fields with few-nanometre spatial and sub-cycle temporal resolutions.

Electron holography and microscopy have long been used to map static electric and magnetic fields. Here, authors establish Lorentz Microscopy of Optical Fields, a new technique that uses the deflection and interference of an electron beam to obtain phase-resolved images of nanoscale optical fields.

Coulomb interactions in free-electron beams are usually seen as an adverse effect. The creation of distinctive number states with one, two, three and four electrons now reveals unexpected opportunities for electron microscopy and lithography from Coulomb correlations.

A silicon nitride microresonator is used for coherent phase modulation of a transmission electron microscope beam, with future applications in combining high-resolution microscopy with spectroscopy, holography and metrology.

Optical excitation is a way to control phase transitions in materials, but it lacks spatial specificity. Now, valley-selective photodoping in a Peierls insulator is demonstrated as a method to optically engineer phase textures with minimal heating.

The coupling between light and relativistic free electrons is enhanced through phase matching of electrons with optical whispering-gallery modes in dielectric microspheres and through extended modal lifetimes.

Attosecond electron pulse trains in electron microscopy are demonstrated through the coupling of phase-locked multicolour optical fields with electron pulses. A new variant of quantum state tomography for free-electron ensembles is established.

The quantum interference of electrons that have been scattered by light has been used to produce holograms of the underlying electromagnetic fields — and might open up methods for studying materials at high temporal and spatial resolution.

Using a technique inspired by Ramsey spectroscopy it is now possible to coherently control free electrons in an electron microscope.

A tracing of the phase-ordering kinetics of a charge density wave system demonstrates the potential of ultrafast low-energy electron diffraction for studying phase transitions and ordering phenomena at surfaces and in low-dimensional systems.

Strong nonlinearities in solid state materials can lead to interesting applications in photonics. Here the authors study chiral high-harmonic generation at SiO₂ and MgO surfaces using bi-circular two-color driving fields and extract information on crystal properties.

Light induced magnetization dynamics can be as fast as few tens of femtoseconds. Here, Zayko et al show ultrafast microscopy based on high-harmonic radiation for direct imaging of ultrafast phenomena and capture femtosecond spin dynamics at the nanoscale.

A structural phase transition from metal to insulator on a solid surface is controlled by an ultrafast sequence of optical pulses.

Time-resolved X-ray scattering is utilized to demonstrate an ultrafast 300 ps topological phase transition to a skyrmionic phase. This transition is enabled by the formation of a transient topological fluctuation state.

Imaging the dynamic behaviour of magnetic textures with high spatial and temporal resolution is challenging. Here, the authors use ultrafast Lorentz microscopy to study the rotational motion of a magnetic vortex core in a permalloy nanoisland, excited by sinusoidal radio-frequency currents.

The coherent manipulation of electron quantum states using light, commonly employed in atoms and molecules, is extended to the case of free electron beams using ultrafast transmission electron microscopy; this approach may enable a range of applications in ultrafast electron imaging and spectroscopy down to attosecond precision.

Photoemission from nanostructures has raised considerable interest in recent years. The authors propose a low-budget scheme for multiphoton photemission with a continuous-wave laser that may inspire design of accessible nanoscale coherent electron sources.