Condensed matter physics at high pressure

Signatures of pressure-induced high-temperature superconductivity in nickelates have sparked great interest in these materials. Here, the sensitivity of Ruddlesden–Popper nickelate formation to in-plane misfit strain is investigated, revealing that tensile strain favours the perovskite structure LaNiO₃, whereas compressive strain stabilizes the La₃Ni₂O₇ phase where high-temperature superconductivity was reported.

The field of hydride superconductivity is currently attempting to increase the critical temperature T_c, while also lowering the required stabilization pressure. Here, L.C. Chen et al. study (Y,Ce)H₉ alloys and find maximum T_c ~ 140 K at 130 GPa pressure.

Recently, high-temperature superconductivity has been reported in LaH₁₀ and CeH₁₀. Here, the authors report superconductivity in the alloy (La,Ce)H_9-10 with T_c = 176 K at 100 GPa, providing an improved compromise between high transition temperature and low pressure requirements.

Superconductivity was recently discovered in the clathrate hydride CeH₉ with superconducting temperature (T_c) of 57 K at pressures below 1 megabar. Here, the authors show that T_c can be increased to 148 K in the substitutional alloy (La,Ce)H₉, while maintaining a pressure below 1 megabar.

Superconductivity at megabar pressures has recently attracted interest in the context of hydrides. Here, the authors demonstrate superconductivity up to 26 K at high pressure in elemental titanium, and further suggest that electron correlations contribute to the high T_c.

The discovery of superconductivity in hydrides at critical temperature (T_c) near room temperature receives intensive attentions. Here the authors report experimental synthesis and discovery of superconductivity with T_c above 210 K in calcium superhydrides at 160–190 GPa.

Long-range magnetic ordering of two-dimensional crystals can be sensitive to interlayer coupling, enabling the effective control of interlayer magnetism. Here, the authors report the pressure-controlled interlayer magnetic coupling of chromiumpyrazine coordinated magnets.

Designing and understanding quantum materials requires continuous feedback between experimental observations and theoretical modelling. Here, a machine learning scheme integrates experiments with theory and modelling on experimental timescales for extracting material parameters and properties of Dy₂Ti₂O₇ spin-ice under pressure.

Elemental tellurium is a natural p-type semiconductor with a chiral structure and spin-polarized Fermi surface. Here, the authors show that the pressure-induced topological change of the Fermi surface at 17 kbar triggers an Anderson-Mott insulator-to-metal transition.

The authors discover high-pressure Sc₂N₆, Sc₂N₈, and ScN₅ polynitrides, synthesized at high pressure and temperature conditions, featuring a unique nitrogen catenation and previously unknown N₆⁶⁻ anions, N₈⁶⁻ anions and anionic corrugated 2D-polynitrogen layers.

The subtle distortion in atomic structure underlies the drastic changes in the properties of amorphous phase-change materials. Here authors show that that pressure can reverse the Peierls-like distortions introduced by temperature, eliciting a polyamorphic transition in GeTe and GeSe.

Dynamic compression experiments enable material studies in regimes relevant for planetary science, but temperature is difficult to measure in these challenging conditions. Here, the authors report on temperature, density, pressure, and structure of dynamically compressed Cu up to 1 TPa determined from extended x-ray absorption fine structure and velocimetry.

The ζ-N₂ phase is key for comprehending the pressure-driven molecular to polymeric shift in nitrogen. Here, the authors resolved the crystal structure of ζ-N₂ and identified a gradual delocalization of its electronic density under pressure, culminating in the initiation of nitrogen’s polymerization.

The progress in generating high static pressures in diamond anvil cells opens opportunities for studying novel materials with unusual properties. Here, the authors report a universal high-pressure diamond edge Raman scale up to 500 gigapascals, which does not require an additional pressure sensor.

Multilayers comprising alternating soft and hard layers offer enhanced toughness compared to all-hard structures. Here authors reveal how the hard and soft components in Ruddlesden–Popper perovskites work cooperatively to resist deformation under pressure, informing the design of alternating superlattices for engineering applications.

Rare-earth hexaborides are of interest for their pressure-induced phase transformations, but further understanding is needed regarding their failure mechanisms. Here, nanoindentation of EuB₆ causes dislocation-mediated shear band formation, driven by the breaking of boron-boron bonds.

The study of materials under extreme conditions can reveal interesting physics in diverse areas such as condensed matter and geophysics. Here, the authors investigate experimentally and theoretically the high pressure-high temperature phase diagram of niobium revealing a previously unobserved phase transition from body-centered cubic to orthorhombic phase.