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

Abstract

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.

Pressure-Quenched Superconductivity in Weyl Semimetal NbP Induced by Electronic Phase Transitions under Pressure

“…26 We attribute this to the probable nanonization of NbP crystal under pressure due to the Hall-Petch-like effect. 27,28 Li et al recently reported how nanonization of particles enhances the superconductivity in the decompression process, 29 which also well-explains the results we observed in electrical-transport measurements. The pressure dependence of the axial ratio with pressure shows a discontinuous point at ∼50 GPa (as shown in Figure 3c), indicating an abnormal intrinsic change in the crystal structure of NbP.…”

Superconductivity Induced by Lifshitz Transition in Pristine SnS2 under High Pressure

“…In the decompression run, the R – T curve gradually degrades into semiconductor behavior, but the T c is enhanced to 5.1 K when the pressure is released to 52.6 GPa, as shown in the Figure S2. The decompression-enhanced or persistent superconductivity has also been reported on some other chalcogenides or pnictides, which is attributed to the irreversibility in grain and structure of pressurized crystals. − For the second run, superconductivity with T c = 3.1 K emerges at 43.7 GPa, and the T c is enhanced to 6.2 K at 82.7 GPa, as shown in Figure c. The temperature dependence of the upper critical field at 70.5 and 82.7 GPa are depicted in Figure d.…”

Impact of Pressure on Structural, Vibrational, and Electrical Properties of Nodal-Line Semimetal HfGe0.92Te

“…Both experimental and theoretical studies have discussed the discontinuous change in the c / a ratio across various materials, which can be ascribed to various driving or coupling factors, encompassing structural differences, stability considerations, transitions in electronic topological phases, , and changes in elastic modulus. , The slight discrepancy between the abnormal pressure values measured by transport data (5–7 GPa) and this observation bears resemblance to the isostructural electronic transition observed in certain other materials. − …”