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Resonant inelastic X-ray scattering interferometry reveals a highly entangled electronic phase in Nd₂Ir₂O₇, enabling extraction of its entanglement structure and confirming the cubic-symmetry-breaking order predicted from complementary Raman spectroscopy.

Novel materials synthesized under extreme conditions can challenge long-held views of fundamental chemistry. Santoro et al. combine fluid CO₂ and solid SiO₂to create a new crystalline compound, via experimentation at ultra-high pressures and temperatures, which is stable at ambient conditions.

Under high pressure, elemental sulfur shows a sharp density discontinuity that evolves with pressure and temperature and terminates at a critical point, indicating a first-order liquid–liquid phase transition.

The nature and stability of carbon dioxide under extreme conditions relevant to the Earth’s mantle is still under debate, in view of its possible role within the deep carbon cycle. Here, the authors perform high-pressure experiments providing evidence that polymeric crystalline CO₂ is stable under megabaric conditions.

The microscopic understanding of photo-induced insulator-to-metal transition (IMT) in 1T-TaS₂ remains elusive. Here, Stahl et al. identify the collapse of interlayer molecular orbital dimers during a collective electronic phase transition as a key mechanism for the IMT in 1T-TaS₂.

Iron in partially molten rocks under deep-mantle conditions partitions into the melt phase less than previously reported, suggesting that melt generated near the core–mantle boundary should segregate upwards.

Chemical elements at high pressure may behave more consistently with their periodic properties than they do at ambient conditions. The authors report the synthesis of PH₃ from black phosphorous and hydrogen, and the crystallization of the van der Waals compound (PH₃)₂H₂ which fills a gap in the chemistry of adjacent elements in the periodic table.

The chemical stability of alkali halides has caused them to be exploited as inert media in high-pressure, high-temperature experiments. Here, NaCl and KCl are unexpectedly found to react with yttrium, dysprosium and iron oxide in a laser-heated diamond anvil cell, producing Y₂Cl, DyCl, Y₂ClC and Dy₂ClC at ~40 GPa and 2000 K and FeCl₂ at ~160 GPa and 2100 K.

Metallic glasses show polyamorphous features, while the nature of the transformation between those amorphous structures is still unclear. Here, Luo et al.propose a pressure-induced hierarchical densification to explain a transformation in Ce-based metallic glass near glass transition temperature.

Investigating the melting curves of transition metals like iridium is vital for understanding planetary cores and advancing high-pressure technology, yet their high-pressure phase diagrams remain poorly understood. Here, the authors use advanced diamond anvil cell techniques and synchrotron X-ray diffraction to map iridium’s phase diagram, confirming its face-centered cubic structure up to 101 GPa and 5600 K, and providing critical data for technological applications.

Molecular models of kerogens provide a detailed picture of their nanostructure in organic-rich shale.

A quantum critical point (QCP) describes a phase change independent of thermal fluctuations and instead can be driven by chemical or hydrostatic pressure. Here, the authors investigate by X-ray diffraction the evolution of the charge density wave in 2H-TaSe₂ as a function of pressure and demonstrate how it is intertwined with a QCP and the superconducting phase of the system.

Polycyclic aromatic hydrocarbons, typically wide-band-gap insulators, may transform into metals under compression, offering potential for interesting electronic properties. Here, a pressure-induced insulator-to-semiconductor transition in dicoronylene was demonstrated, achieving a resistivity drop at 23.0 GPa, and a mechanism was proposed for this transition, paving the way for hydrocarbon-based molecular metals.

Geochemically relevant [C₄O₁₀]^4- pyramids are the most polymerized high pressure carbonate units, with Mn-, Cd-, Ca- and Ba-based structures reported to date. Here, the authors synthesized an Fe-carbonate featuring [C₄O₁₀]^4- anions with a predicted high-to-low-spin crossover at unusually high pressure near 95 GPa.

The transition metal dichalcogenide IrTe₂ is a candidate system to realise topological superconductivity, a sought-after state which could host Majorana fermions, and hence is of interest to the field of quantum computing. Here, the authors combine high-pressure X-ray diffraction and DFT calculations to investigate the evolution in the crystal- and electronic structure of IrTe₂ as a function of pressure, highlighting the role of the Te-Ir-Te bond angle.