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Layered van der Waals (vdW) dichalcogenides are distinguished by their unique crystal structures and high structural tunability, rendering them suitable for applications in optics and optoelectronics. Despite significant processes, some fundamental questions remain in two-dimensional (2D) vdW dichalcogenides, such as clarifying detailed structure–property relationship and further improving the optoelectronic performance. Herein, by applying pressure to tune the crystal structure in 2D vdW dichalcogenide SiTe2, we realized a five orders of magnitude boost in photocurrent at 8 GPa. Such an enhancement is attributed to bandgap narrowing and an increased carrier concentration. Furthermore, bandgap closing and metallization were observed at 15.4 GPa, further suggesting the significant change of electronic structure upon compression. This study not only elucidates the intriguing pressure-induced behavior of SiTe2 but also paves the way for harnessing the unique pressure-responsive properties of 2D vdW dichalcogenides in advanced optoelectronic systems. [ABSTRACT FROM AUTHOR]

A material described as lutetium–hydrogen–nitrogen (Lu-H-N in short) was recently claimed to have "near-ambient superconductivity" [Dasenbrock-Gammon et al., Nature 615, 244–250 (2023)]. If this result could be reproduced by other teams, it would be a major scientific breakthrough. Here, we report our results of transport and structure measurements on a material prepared using the same method as reported by Dasenbrock-Gammon et al. Our x-ray diffraction measurements indicate that the obtained sample contains three substances: the face-centered-cubic (FCC)-1 phase (Fm-3m) with lattice parameter a = 5.03 Å, the FCC-2 phase (Fm-3m) with a lattice parameter a = 4.755 Å, and Lu metal. The two FCC phases are identical to the those reported in the so-called near-ambient superconductor. However, we find from our resistance measurements in the temperature range from 300 K down to 4 K and the pressure range 0.9–3.4 GPa and our magnetic susceptibility measurements in the pressure range 0.8–3.3 GPa and the temperature range down to 100 K that the samples show no evidence of superconductivity. We also use a laser heating technique to heat a sample to 1800 °C and find no superconductivity in the produced dark blue material below 6.5 GPa. In addition, both samples remain dark blue in color in the pressure range investigated. [ABSTRACT FROM AUTHOR]

Palladium hydrides (PdHx) have important applications in hydrogen storage, catalysis, and superconductivity. Because of the unique electron subshell structure of Pd, quenching PdHx materials with more than 0.706 hydrogen stoichiometry remains challenging. Here, the 1:1 stoichiometric PdH (Fm3¯m)$Fm\bar{3}m)$ is successfully synthesized using Pd nano icosahedrons as a starting material via high‐pressure cold‐forging at 0.2 GPa. The synthetic initial pressure is reduced by at least one order of magnitude relative to the bulk Pd precursors. Furthermore, PdH is quenched at ambient conditions after being laser heated ≈2000 K under ≈30 GPa. Corresponding ab initio calculations demonstrate that the high potential barrier of the facets (111) restricts hydrogen atoms' diffusion, preventing hydrogen atoms from combining to generate H2. This study paves the way for the high‐pressure synthesis of metal hydrides with promising potential applications. [ABSTRACT FROM AUTHOR]

As promising photovoltaic materials, halide perovskites display large structural modifiability specific to their organic‐inorganic hybrid lattices, thus providing key to unlock many enhanced and novel physical properties. In particular, hybrid perovskites exhibit extraordinary functional responses to mechanical stimulation due to their soft lattices. However, a general pattern describing the evolution of perovskite properties under pressure is missing, rendering such research without theoretical guidance and further the optimization of optoelectronic performance. Here, a framework delineating the pressure‐dependent evolutions of lattice structure, bandgap, and photoluminescence (PL) across four distinct regions in all perovskites assuming 3D and 2D structures is unveiled, accrediting long‐range disorderness to be the common origin of bandgap blueshift, PL annihilation, and structural amorphization. Using such developed model as an instructional guideline, an optical bandgap and luminescent evolutions in quasi‐2D tin(II) iodide perovskites are revealed, where (C4H9NH3)2(CH3NH3)Sn2I7 (C4H9NH3+: butylammonium; CH3NH3+: methylammonium) is found to be the softest perovskite (bulk modulus ≈4.8 GPa) known so far. By meticulously choosing appropriate peak pressure ≈4 GPa, (C4H9NH3)2(CH3NH3)Sn2I7 shows irreversible defect healing (carrier lifetime prolongation from 7 to 22 ns) and permanent PL enhancement upon decompression to ambient condition, signifying practicality of the pressure‐driven behaviors unveiled in this work. [ABSTRACT FROM AUTHOR]

Layered van der Waals (vdW) dichalcogenides are distinguished by their unique crystal structures and high structural tunability, rendering them suitable for applications in optics and optoelectronics. Despite significant processes, some fundamental questions remain in two-dimensional (2D) vdW dichalcogenides, such as clarifying detailed structure–property relationship and further improving the optoelectronic performance. Herein, by applying pressure to tune the crystal structure in 2D vdW dichalcogenide SiTe2, we realized a five orders of magnitude boost in photocurrent at 8 GPa. Such an enhancement is attributed to bandgap narrowing and an increased carrier concentration. Furthermore, bandgap closing and metallization were observed at 15.4 GPa, further suggesting the significant change of electronic structure upon compression. This study not only elucidates the intriguing pressure-induced behavior of SiTe2 but also paves the way for harnessing the unique pressure-responsive properties of 2D vdW dichalcogenides in advanced optoelectronic systems. [ABSTRACT FROM AUTHOR]