Superconductivity in Layered van der Waals Hydrogenated Germanene at High Pressure

TL;DR

This study investigates the superconducting properties of layered van der Waals hydrogenated germanene (GeH) under high pressure, revealing pressure-induced phase transitions and enhanced superconductivity linked to increased density of states and phonon softening.

Contribution

It provides new insights into high-pressure superconductivity in amorphous layered hydrides, specifically GeH, combining experimental and theoretical analysis.

Findings

Superconductivity at 5.41 K at 8.39 GPa

Crystalline to amorphous transition at 16.80 GPa

Enhanced Tc up to 6.1 K during decompression

Abstract

Structural and superconducting transitions of layered van der Waals (vdW) hydrogenated germanene (GeH) were observed under high-pressure compression and decompression processes. GeH possesses a superconducting transition at critical temperature (Tc) of 5.41 K at 8.39 GPa. A crystalline to amorphous transition occurs at 16.80 GPa while superconductivity remains. An abnormally increased Tc up to 6.1 K has been observed in the decompression process while the GeH remained amorphous. Thorough in-situ high-pressure synchrotron X-ray diffraction and in-situ high-pressure Raman spectroscopy with the density functional theory simulations suggest that the superconductivity of GeH should be attributed to the increased density of states at the Fermi level as well as the enhanced electron-phonon coupling effect under high pressure. The decompression-driven superconductivity enhancement arises from pressure-induced phonon softening related to an in-plane Ge-Ge phonon mode. As an amorphous metal hydride superconductor, GeH provides a platform to study amorphous hydride superconductivity in layered vdW materials.