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Nonlinear phononics is a method for creating transient structural changes in solids, but its effect is limited to the region of optical excitation. Now, coupling to a propagating polariton allows nonlinear phononics to drive a nonlocal response.

Intense light pulses can induce symmetry breaking, as for the generation of ferroelectricity in SrTiO₃. Using ultrafast X-ray diffuse scattering at a free-electron laser, nonlinear phonon interactions that occur on such mid-IR excitation are observed, with a theory for the dynamics presented.

There is evidence that K₃C₆₀ can host a photo-induced superconducting state. Now, resonant excitation at low frequencies allows this phenomenon at room temperature and low pumping fluence.

Despite exhibiting ferroelectric features, SrTiO₃ fails to display long-range polar order at low temperatures due to quantum fluctuations. An ultrafast X-ray diffraction experiment now probes polar dynamics of this material at the nanometre scale.

All-optical, mode-selective manipulation of the crystal lattice can be used to enhance and stabilize ferromagnetism in YTiO₃ well above its equilibrium ordering temperature and for many nanoseconds, enabling dynamic engineering of practically useful non-equilibrium functionalities in fluctuating electronic systems.

The dynamics of the magnetic correlations after photo-doping Sr₂IrO₄ are studied through ultrafast time-resolved resonant inelastic X-ray spectroscopy. The timescales are found to depend on the dimensionality of the correlations.

Light can be used to directly excite phonon modes in condensed matter. Simultaneously exciting several modes in an antiferromagnetic rare-earth orthoferrite drives behaviour that mimics the application of a magnetic field.

Light can interact with the electrons in a crystalline solid, which in turn generates lattice vibrations or phonons. A related phenomenon was proposed 40 years ago in which it is the ions in the crystal rather than the electrons that mediate the interaction. This effect, known as ionic Raman scattering, is now observed experimentally.

Large-amplitude, infrared-active vibrations excited in a LaAlO₃ substrate induce magnetic order melting in a NdNiO₃ film. The melt front initiated at the interface propagates in the film at supersonic speeds, likely to be driven by electronic processes.

Time- and momentum-resolved spectroscopy gives dynamical information on complex materials, enabling disentanglement of their coupled degrees of freedom. Using time-resolved X-ray diffraction at a free electron laser, Leeet al. investigate the charge order parameter in a striped nickelate.

Femtosecond X-ray diffraction and ab initio density functional theory calculations are used to determine the crystal structure of YBa₂Cu₃O_6.5 undergoing optically driven, nonlinear lattice excitation above the transition temperature of 52 kelvin, under which conditions the electronic structure of the material changes in such a way as to favour superconductivity.

Ultrashort mid-infrared laser pulses can drive atoms far from their equilibrium positions in LiNbO₃, exciting high phonon harmonics and providing a way to map the interatomic potential.

A spectroscopic study of strontium titanate provides a method for transferring the vibrational energy of a low-frequency phonon mode to higher-frequency modes, with the potential to access elusive ‘silent’ modes.