Exploring functionalities under high-pressure conditions represents a promising frontier in materials discovery. Because molecules in organic crystals form packing structures through weak intermolecular forces such as van der Waals interactions, their intermolecular distances can readily adjust in response to compression. In most luminescent π-conjugated molecules, this compression typically enhances nonradiative decay pathways, resulting in reduced emission intensity. Here, however, we report that applying pressure to single crystals of a phenanthrene-based derivative introduced with an anthracene unit yields an unusual pressure-induced emission enhancement up to about 1.5 GPa. Furthermore, as pressure increases to 3.5 GPa, the emission peak exhibits a large red shift, by 131 nm, corresponding to an exceptionally high-pressure sensitivity of 37.4 nm/GPa. This sensitivity is the largest value among molecular materials to date.

Advancements in high pressure generation technology through static compression have pioneered new frontiers in high pressure science. While the double-stage diamond anvil cell (ds-DAC) and the toroidal-type DAC (t-DAC) were developed as means to exceed the pressure generation limits of conventional DACs, their ability to generate extreme pressures exceeding Earth's central pressure is not necessarily highly reproducible. Here, we report results from pressure generation experiments using a DAC with a semi-ball-like tip shape (st-DAC). The gradual change in bevel angle provides a gentle pressure gradient at the culet edge and supports the protrusion through an effective confining pressure at the base. The st-DAC achieved pressures exceeding 400 GPa with high reproducibility, even when the pressure difference relative to the periphery reached 250-300 GPa without failure. For a 5 mu m culet size, it enabled the generation of up to 500 GPa.

We investigate the distorted face-centered-cubic (dfcc) phase of yttrium (Y) using a data-assimilation-based structure search that combines high-resolution powder x-ray diffraction (XRD) data with machine-learning interatomic potentials. By exploring supercells containing up to 128 atoms, we identify three low-enthalpy phases: the previously reported I4_1/a structure and two additional structures, Ibam and R3. No data-assimilation-derived structure relaxes to the previously proposed R3m phase. Phonon calculations show that I4_1/a, Ibam, and R3 are dynamically stable, whereas R3m exhibits imaginary modes near the Γ point, indicating dynamical instability. Enthalpy calculations using both PBE and r^2SCAN place the four candidate structures within about 10 meV/atom, indicating a complex energy landscape with multiple competing minima, although R3m is consistently highest in enthalpy and r^2SCAN favors I4_1/a throughout the dfcc pressure range. Rietveld refinements of the powder XRD profile at 60 GPa further narrow the viable structural models to I4_1/a and Ibam, both of which reproduce the experimental data better than R3m and R3. Taken together with the energetic ordering and dynamical stability, these results identify I4_1/a as the most plausible structure of the dfcc phase of Y, with Ibam remaining a close competing candidate, particularly toward the high-pressure side of the dfcc region.

Reducing the stabilization pressure of superhydrides represents one of the most important challenges in hydrogen-saturated compound chemistry. Moving in this direction, we studied the Ba-Si-H system at 0-142 GPa using transport measurements, 1H nuclear magnetic resonance, single-crystal and powder X-ray diffraction in the temperature range of 4-317 K. We synthesized the previously predicted cubic BaSiH_8 at pressures of 18-31 GPa. Remarkably, we demonstrate that BaSiH_8 remains stable upon decompression to ambient conditions and can be recovered from the diamond anvil cell. Obtained Ba-Si polyhydrides exhibit metallic and superconducting properties (T_c = 9 K, B_c2(0)=13-16 T) at 142 GPa. However, at pressures below 50 GPa, these hydrides behave as degenerate semiconductors (bandgap < 0.4 meV) or poor metals with weak electron localization, negative magnetoresistance, photovoltaic effect, and persistent photoconductivity in the X-ray and visible range. Our work demonstrates the high-pressure synthesis of Ba-Si polyhydrides that remain stable upon decompression to ambient conditions, overcoming a critical bottleneck in superhydride chemistry and establishing a foundation for practical applications in hydrogen storage.

Thickness and pressure cooperatively modulate the transport properties in layered materials─particularly two-dimensional (2D) superconductivity─which are intrinsically governed by quantum confinement and anisotropic interactions. Here, through systematic investigation of thickness-dependent pressure-induced phenomena in black phosphorus, we reveal the mechanism by which dimensional confinement governs metallization and superconductivity via modulation of the electronic structure. Robust 2D superconductivity, observed in both few-layer samples and nanoflakes within the bulk, underscores quantum confinement as the fundamental origin of 2D superconductivity. Furthermore, the 3D-2D crossover in bulk highlights the critical role of weak interlayer coupling in stabilizing 2D superconducting behavior. Remarkably, quantum confinement dramatically enhances the critical field, with the in-plane critical field in 6-layer sample exceeding the Pauli limit due to enhanced spin-orbit scattering. These findings provide new insights into engineering superconducting dimensionality and properties via combined thickness and pressure control.

Extreme high-pressure generation beyond the Earth's central pressure is currently achieved by static compression. The high-pressure technology is a key not only for the condensed matter physics but also for the earth and planetary science to understand the interior of planets larger than the Earth such as gas/ice giants and exoplanets. On the other hand, how to determine the pressure generated is another fundamental issue. There are many kinds of pressure standards, and their mutual consistency under extreme pressure conditions is not yet known. Here we report the volumetric (density) interrelationships of seven metals (Fe, Cu, Mo, W, Re, Pt, Au) and two non-metal materials (MgO, NaCl) based on simultaneous static compression experiments up to similar to 430 GPa, including previously reported static compression experiments. Present results reveal the fact that even on latest pressure scales by shock-less dynamic compression studies not all of them necessarily agree within the error limit under extreme high-pressure conditions. Our internally consistent equations of state bridge various extreme pressure sciences and realize comprehensive discussions.

The discovery of 15.1 K superconductivity in first-stage CaC_{6} reignited interest in searching for high-temperature superconductors in graphite intercalation compounds (GICs). However, despite nearly two decades of intensive research, progress in exploring high-temperature superconductivity in GIC materials has remained stagnant. Currently, research on the superconductivity of GICs mainly focuses on first-stage GICs, while the superconductivity of high-stage GICs has been largely overlooked. Here, we report an experimental discovery of superconductivity with maximum critical temperature (T_{c}) of approximately 28 K in sodium carbide at about 14 GPa evidenced by a sharp drop of resistance and a characteristic decrease of T_{c} under magnetic fields up to 6 T. The upper critical field μ_{0}H_{c2}(0) was estimated to be 8.8 T based on fitting with the Ginzburg-Landau superconducting model while the coherent length is approximately 61.2  Å. X-ray diffraction measurements combined with crystal structure predictions identified the superconducting candidate material as the second-stage GIC NaC_{8}, in which sodium atoms occupy the interlayer spaces between AA-stacked bilayer graphene. The current findings not only achieve the long-sought high-T_{c} GICs, but more importantly, open up a new avenue for exploring high-temperature superconductors in light-element compounds.

Quantum spin liquid states have garnered significant attention as potential precursors for high-temperature superconductors. Researchers are aiming to achieve high-temperature superconductivity through regulation. However, previous studies have indicated that candidate materials with honeycomb structures, such as Na2IrO3 and alpha-Li2IrO3, remain in a magnetically ordered and insulating state. Pressure serves as an effective regulatory tool by adjusting atomic interactions through interatomic spacing manipulation, thereby influencing the band structure near the Fermi surface and consequently tuning quantum-state evolution. In this study, interlayer Li were substituted by Ag atoms in alpha-Li2IrO3 to obtain the Ag3LiIr2O6, and its transitions in structure and physical properties as functions of temperature and pressure were investigated. It has been observed that Ag3LiIr2O6 remains stable between -190 and 300(degrees)C without undergoing any structural phase transitions. High-pressure phase transitions occur at 3.0-7.5 and 12.0-16.1 GPa. The first structural phase transition, as deduced from high-pressure x-ray diffraction and Raman spectroscopy, is associated with Ir-Ir dimerization and IrO6 octahedral distortion. Corresponding resistance measurements indicate a decreasing rate reduction in resistance near 5.2 GPa due to dimerization. Further compression leads to the existence of a minimum room-temperature resistance at similar to 19.5 GPa. A transition from negative to positive magnetoresistance occurs at 12.4 GPa under 2 K. Further analysis suggests that the transition from negative to positive magnetoresistance may be connected to the valence change of Ag from +1 to 0. Although the desired insulator-to-metal transition was not achieved, we have explored the correlation between structural and physical property transitions under high pressure, laying the groundwork for future investigations.

A new method for synthesis of metal polyhydrides via high-pressure thermal decomposition of corresponding amidoboranes in diamond anvil cells is proposed. Within this approach, molecular semiconducting cesium (P4/nmm-CsH7, P1-CsH15+x) and rubidium (RbH9-x) polyhydrides with a very high hydrogen content reaching 93 at.% are synthesized. Preservation of CsH7 at near ambient conditions, confirmed both experimentally and theoretically, represents a significant advance in the stabilization of hydrogen-rich compounds. In addition, two crystalline modifications of RbH9-x with pseudohexagonal and pseudotetragonal structures identified by synchrotron X-ray diffraction, and Raman measurements are synthesized. Both phases are stable at 8-10 GPa. This is an unprecedentedly low stabilization pressure for polyhydrides. These discoveries open up possibilities for modifying existing hydrogen storage materials to increase their efficiency. How to increase the hydrogen content in metal hydrides? A possible solution is to prepare them at high pressure from metal amidoboranes and then decompress the reaction products. In this way, cesium (CsH7, CsH15-17) and rubidium (RbH8-9) polyhydrides with a hydrogen content up to 93 at.% are synthesized. These compounds remain stable near or even below 10 GPa. image

Electrical resistivity measurements on oriented FeTiO 3 ilmenite using single crystals at high pressures proves that FeTiO 3 ilmenite shows anisotropic electrical resistivity. The resistivity in the direction perpendicular to the c -axis decreased monotonously with increasing pressure. In contrast, the resistivity in the parallel direction to the c -axis initially decreased and slightly increased with increasing pressure above 6 GPa. It then resumed decreasing above 8 GPa. The hallow-shape of the curvature was observed. Neutron and synchrotron X-ray diffraction experiments provided an accurate picture of the pressure-induced changes of the FeTiO 3 ilmenite structure. FeTiO 3 transforms neither into perovskite nor LiNbO 3 phase under pressures up to 28 GPa. However, different compression curves were observed for both FeO 6 and TiO 6 octahedra below 8 GPa. FeO 6 is more compressible and flexible than TiO 6 . Among Fe–Fe, Ti–Ti and Fe–Ti interatomic distances, the shortest Fe–Ti distance presents the highest electrical restivity and electron mobility according to Fe 2+ Ti 4+ and Fe 3+ Ti 3+ by electron super-exchange mechanism, which is enhanced during compression. At high pressure, the electron configuration of Fe 2+ (3 d 6 ) is more strongly changed than Ti 4+ (3 d 0 ) and the former cation is the emphasized by Jahn–Teller effect in the ligand field of C 3 v molecular symmetry. The anisotropic electrical resistivity and non-uniform structure change of Fe–Ti interatomic distance can be explained by possible spin transition. The spin transition of Fe Kβ from high-spin to intermediate-spin state is possible in the electronic state change of FeTiO 3 .

The search for high-temperature superconducting superhydrides has recently moved into a new phase by going beyond extensively probed binary compounds and focusing on ternary ones with vastly expanded material types and configurations for property optimization. Theoretical and experimental works have revealed promising ternary compounds that superconduct at or above room temperature, but it remains a pressing challenge to synthesize stoichiometric ternary compounds with a well-resolved crystal structure that can host high-temperature superconductivity at submegabar pressures. Here, we report on the successful synthesis of ternary LaBeH_{8} obtained via compression in a diamond anvil cell under 110-130 GPa. X-ray diffraction unveils a rocksalt-like structure composing La and BeH_{8} units in the lattice. Transport measurements determined superconductivity with critical temperature T_{c} up to 110 K at 80 GPa, as evidenced by a sharp drop of resistivity to zero and a characteristic shift of T_{c} driven by a magnetic field. Our experiment establishes the first superconductive ternary compound with a resolved crystal structure. These findings raise the prospects of rational development of the class of high-T_{c} superhydrides among ternary compounds, opening greatly expanded and more diverse structural space for exploration and discovery of superhydrides with enhanced high-T_{c} superconductivity.

This paper examines the micro-parameters of superconductors. It studies the modulations from weak van der Waals interaction to strong covalence bonding of superconductors. In particular, we studied layered black phosphorus (BP) as a function of pressure. These results reveal a rich scenario of phase transitions and related quantum phenomena, which show that the phases exhibit superconducting states at a pressure higher than 5.0 GPa. In addition, they indicate an angle-dependent upper critical field that demonstrates the dimensional characteristics of superconductivities. This result suggests that the A17 and cubic phases are three-dimensional (3D). The A7 phase shows a two-dimensional (2D) character. The 2D behavior is related to a weakened, distorted, entangled interlayer coupling.

Magnetic and structure transitions of Mn 3–x Fe x O 4 solid solutions under extreme conditions are clarified by neutron time-of-flight scattering diffraction and X-ray Mössbauer measurement. The ferrimagnetic-to-paramagnetic transition temperature (100 °C) of Mn 2 FeO 4 spinel is different from the tetragonal-to-cubic structure transition temperature (180 °C). The structure transition temperature decreases with increasing pressure. The transition is not coupled with the magnetic transition. Synchrotron X-ray Mössbauer experiments have revealed the pressure effects on the distribution of Fe 2+ and Fe 3+ at the tetrahedral and octahedral sites in the spinel structure. Ferrimagnetic MnFe 2 O 4 and Mn 2 FeO 4 spinels show sextet spectral features with hyperfine structure elicited by internal magnetic fields. Cubic MnFe 2 O 4 spinel and tetragonal Mn 2 FeO 4 transform to high-pressure orthorhombic postspinel phase above pressures of 18.4 GPa and 14.0 GPa, respectively. The transition pressure decreases with increasing Mn content. The postspinel phase has a paramagnetic property. Mn 2 O 10 dimers of two octahedra are linked via common edge in three dimentional direction. The occupancy of Fe 2+ in the tatrahedral site is decreased with increasig pressure, indicating more oredered structure. Consequently, the inverse parameter of the spinel structure is increased with increasing pressure. The magnetic structure refinements clarify the paramagnetic and ferrimagnetic structure of MnFe 2 O 4 and Mn 2 FeO 4 spinel as a function of pressure. The magnetic moment is ordered between A and B sites with the anti-parallel distribution along the b axis. The nuclear tetragonal structure ( a N , a N , c N ) has the ferrimagnetic structure but the orthorhombic magnetic structure has the ferrimagnetic structure with the lattice constants ( a M , b M , c M ). The magnetic moment is ordered between A and B sites with the anti-parallel distribution along the b M axis.

Quantum spin liquid (QSL) state has attracted a great deal of attention as a precursor of high-temperature superconductor. The promising QSL candidates such as ??-RuCl3, Na2IrO3 and ??-Li2IrO3 with honeycomb structure are insulators or semiconductors. An insulator-metal transition (IMT) is necessary for hosting superconducting state. However, all of them have a robust insulating state, even under pressure. Here, an alternative candidate of QSL, Cu2IrO3 is investigated under high pressure and low temperature through x-ray diffraction and electric properties measurement. A dimerization occurs at 7.1 GPa which is similar to ??-RuCl3 and ??-Li2IrO3, accompanied with an anomaly of resistance at -5.0 GPa. The IMT appears under a pressure of -13.8 GPa, which is absent in ??-RuCl3, Na2IrO3 and ??-Li2IrO3 under pressure. It is related to the crystal structure transition at -11.1 GPa, which induces the decline of interlayer distance. Furthermore, a strange crossover from negative to positive magnetoresistance is observed under pressure of 21.8 to 24.2 GPa at 2 K. This may be due to the valence change of Cu+ to Cu2+, as a result of the decreasing of interlayer distance and the shortening of O???Cu???O bond under pressure.

Abstract Polyhydrides are a novel class of superconducting materials with extremely high critical parameters, which is very promising for applications. On the other hand, complete experimental study of the magnetic phase diagram for the best so far known superconductor, lanthanum decahydride LaH10, encounters a serious complication because of the large upper critical magnetic field HC2(0), exceeding 120–160 T. Partial replacement of La atoms by magnetic Nd atoms results in a decrease of the upper critical field, which makes it attainable for existing pulse magnets. We found that addition of neodymium leads to significant suppression of superconductivity in LaH10: each atomic % of Nd causes decrease in TC by 10–11 K. Using strong pulsed magnetic fields up to 68 T, we constructed the magnetic phase diagram of the ternary (La,Nd)H10 superhydride, which appears to be surprisingly linear with HC2 ∝ |T – TC|. The pronounced suppression of superconductivity in LaH10 by magnetic Nd atoms and the robustness of TC with respect to nonmagnetic impurities (e.g., Y, Al, C) under Anderson’s theorem indicate the isotropic (s‑wave) character of conventional electron-phonon pairing in the synthesized superhydrides.

Polyhydrides are a novel class of superconducting materials with extremely high critical parameters, which is very promising for sensor applications. On the other hand, a complete experimental study of the best so far known superconductor, lanthanum superhydride LaH10, encounters a serious complication because of the large upper critical magnetic field HC2(0), exceeding 120–160 T. It is found that partial replacement of La atoms by magnetic Nd atoms results in significant suppression of superconductivity in LaH10: each at% of Nd causes a decrease in TC by 10–11 K, helping to control the critical parameters of this compound. Strong pulsed magnetic fields up to 68 T are used to study the Hall effect, magnetoresistance, and the magnetic phase diagram of ternary metal polyhydrides for the first time. Surprisingly, (La,Nd)H10 demonstrates completely linear HC2(T) ∝ |T – TC|, which calls into question the applicability of the Werthamer–Helfand–Hohenberg model for polyhydrides. The suppression of superconductivity in LaH10 by magnetic Nd atoms and the robustness of TC with respect to nonmagnetic impurities (e.g., Y, Al, C) under Anderson's theorem gives new experimental evidence of the isotropic (s‐wave) character of conventional electron–phonon pairing in lanthanum decahydride.

The discovery of clathrate superhydrides has approached the long-standing dream of room-temperature superconductivity and thus inspired their prosperous research under high pressure. However, how to experimentally optimize these compelling superhydrides is still a formidable challenge. Here, we find that half of the Ce atoms in the recently discovered hexagonal close packed (hcp) CeH9 structure can be randomly replaced by adjacent La, resulting in the formation of LaH9 unit that is impossible in a binary system. Our experiments show that hcp (La, Ce)H9 can be synthesized at ~110 GPa and possesses a maximum Tc of 178 K at higher pressure, which is evidenced by in-situ X-ray diffraction and electronic transport measurement where a sharp drop of resistivity to zero and a characteristic decrease of Tc under a magnetic field up to 9 T. More importantly, the Tc of (La, Ce)H9 is significantly increased by ~50-80 K compared to CeH9, showing the hitherto highest Tc at megabar pressure. Our experimental results not only verify the feasibility of improving the superconductivity of hydrides by introducing other suitable metals, but also provide important inspiration for finding high-Tc superconductors in various multinary superhydrides.