Superconducting Phase Induced by a Local Structure Transition in Amorphous Sb_{2}Se_{3} under High Pressure

Deviatoric stress-induced metallization, layer reconstruction and collapse of van der Waals bonded zirconium disulfide

In contrast to two-dimensional (2D) monolayer materials, van der Waals layered transition metal dichalcogenides exhibit rich polymorphism, making them promising candidates for novel superconductor, topological insulators and electrochemical catalysts. Here, we highlight the role of hydrostatic pressure on the evolution of electronic and crystal structures of layered ZrS2. Under deviatoric stress, our electrical experiments demonstrate a semiconductor-to-metal transition above 30.2 GPa, while quasi-hydrostatic compression postponed the metallization to 38.9 GPa. Both X-ray diffraction and Raman results reveal structural phase transitions different from those under hydrostatic pressure. Under deviatoric stress, ZrS2 rearranges the original ZrS6 octahedra into ZrS8 cuboids at 5.5 GPa, in which the unique cuboids coordination of Zr atoms is thermodynamically metastable. The structure collapses to a partially disordered phase at 17.4 GPa. These complex phase transitions present the importance of deviatoric stress on the highly tunable electronic properties of ZrS2 with possible implications for optoelectronic devices.

Pressure-induced disorder and nanosizing inhibits superconductivity in In2Te3

The generation of disorder often gives rise to profound and irreversible physical phenomena. Here, we explore the influence of disorder on the superconducting properties of In2Te3through comprehensive high-pressure investigations. Building upon previous findings, we investigated the progressive suppression of superconductivity in In2Te3during the depressurization process: the increased disorder that ultimately leads to the complete disappearance of the superconducting state. Simultaneously, our high-pressure x-ray diffraction analysis reveals an irreversible structural phase transition. Furthermore, microstructure analysis using transmission electron microscopy clearly demonstrates both grain refinement and a substantial enhancement of disorder. These findings not only provide valuable insights into the mechanism by which disorder suppresses superconductivity, but also offer guidance for future advancements in the fabrication of atmospheric-pressure superconductors.

Creating superconductivity in WB2 through pressure-induced metastable planar defects

High-pressure electrical resistivity measurements reveal that the mechanical deformation of ultra-hard WB₂ during compression induces superconductivity above 50 GPa with a maximum superconducting critical temperature, T_cof 17 K at 91 GPa. Upon further compression up to 187 GPa, the T_cgradually decreases. Theoretical calculations show that electron-phonon mediated superconductivity originates from the formation of metastable stacking faults and twin boundaries that exhibit a local structure resembling MgB₂ (hP3, space group 191, prototype AlB₂). Synchrotron x-ray diffraction measurements up to 145 GPa show that the ambient pressure hP12 structure (space group 194, prototype WB₂) continues to persist to this pressure, consistent with the formation of the planar defects above 50 GPa. The abrupt appearance of superconductivity under pressure does not coincide with a structural transition but instead with the formation and percolation of mechanically-induced stacking faults and twin boundaries. The results identify an alternate route for designing superconducting materials.

Metallization and Superconductivity in the van der Waals Compound CuP2Se through Pressure-Tuning of the Interlayer Coupling

Emergent layered Cu-bearing van der Waals (vdW) compounds have great potentials for use in electrocatalysis, lithium batteries, and electronic and optoelectronic devices. However, many of their alluring properties such as potential superconductivity remain unknown. In this work, using CuP₂Se as a model compound, we explored its electrical transport and structural evolution at pressures up to ∼60 GPa using both experimental determinations and ab initio calculations. We found that CuP₂Se undergoes a semiconductor-to-metal transition at ∼20 GPa at room temperature and a metal-to-superconductor transition at 3.3-5.7 K in the pressure range from 27.0 to 61.4 GPa. At ∼10 and 20 GPa, there are two isostructural changes in the compound, corresponding to, respectively, the emergence of the interlayer coupling and start of interlayer atomic bonding. At a pressure between 35 and 40 GPa, the vdW layers start to slide and then merge, forming a new phase with high coordination numbers. We also found that the Bardeen-Cooper-Schrieffer (BCS) theory describes quite well the pressure dependence of the critical temperature despite occurrence of a possible medium-to-strong electron-phonon coupling, revealing the determinant roles of the enhanced bulk modulus and electron density of states at high pressure. Moreover, nanosizing of CuP₂Se at high pressure further increased the critical temperature even at sizes approaching the Anderson limit. These findings would have important implications for developing novel applications of layered vdW compounds through simple pressure tuning of the interlayer coupling.