Pressure-Induced Effects on the Structure of the FeSe Superconductor

TL;DR

This study investigates how hydrostatic pressure affects the crystal structure of FeSe superconductor, revealing anisotropic compression and changes in key bond angles up to 0.6 GPa.

Contribution

It provides detailed insights into pressure-induced structural changes in FeSe using neutron diffraction, highlighting anisotropic compressibility and bond angle variations.

Findings

FeSe structure is highly compressible with a bulk modulus of 31-33 GPa.

Compression is anisotropic, with greater c-axis compression.

Key bond angles in FeSe pyramids and tetrahedra change under pressure.

Abstract

A polycrystalline sample of FeSe, which adopts the tetragonal PbO-type structure (P4/nmm) at room temperature, has been prepared using solid state reaction. We have investigated pressure-induced structural changes in tetragonal FeSe at varying hydrostatic pressures up to 0.6 GPa in the orthorhombic (T = 50 K) and tetragonal (T = 190 K) phases using high resolution neutron powder diffraction. We report that the structure is quite compressible with a Bulk modulus around 31 GPa to 33 GPa and that the pressure response is anisotropic with a larger compressibility along the c-axis. Key bond angles of the SeFe4 pyramids and FeSe4 tetrahedra are also determined as a function of pressure.