Anomalous compressibility behavior of chromium monoaresenide under high pressure

TL;DR

This study investigates the high-pressure structural behavior of CrAs, revealing anomalous lattice parameter changes and an isostructural phase transition around 0.35 GPa, with implications for its superconductivity.

Contribution

It provides detailed high-pressure XRD analysis of CrAs, identifying anomalous compressibility and a pressure-induced phase transition, advancing understanding of structure-superconductivity relations.

Findings

Lattice parameters a and c first increase then decrease with pressure.

A pressure-induced isostructural phase transition occurs around 0.35 GPa.

Compressibility is highly anisotropic, with b-axis being most compressible.

Abstract

CrAs was firstly observed possessing the bulk superconductivity (Tc~2 K) under high pressure (0.8 GPa) in the very recent work (Wei Wu, et al. Nature Communications 5, 5508 (2014)). To explore the correlation between the structure and the superconductivity, the high-pressure structure evolution of CrAs was investigated using angle dispersive X-ray diffraction (XRD) method with small steps of ~0.1 GPa in a diamond anvil cell (DAC) up to 1.8 GPa. In the pressure range covered by our current experiment, the structure of CrAs keeps stable. However, the lattice parameters exhibit anomalous compression behaviors. With the pressure increasing, the lattice parameters a and c both show a process of first increasing and then decreasing, and the lattice parameter b goes through a quick contract at 0.35 GPa, which suggests a pressure-induced isostructural phase transition occurs in CrAs around this pressure point. Above the phase transition pressure, the axial compressibilities of CrAs present remarkable anisotropy. The compressibilities along the a- and c-axis are about an order of magnitude smaller than that along the b-axis, which is closely related to the different stacking modes in CrAs6 octahedron along different crystallographic axes. A schematic band model was used for addressing above anomalous compression behavior in CrAs.