Phase separation and stripe patterns in K0.8Fe1.6+xSe2 superconductors

TL;DR

This study investigates the microstructural phase separation and stripe patterns in K0.8Fe1.6+xSe2 superconductors, revealing coexisting phases, nano-scale separation, and percolation effects that influence superconductivity.

Contribution

It provides detailed characterization of phase separation and stripe patterns in K0.8Fe1.6+xSe2, highlighting the role of anisotropic assembly and nano-scale heterogeneity.

Findings

Identification of two coexisting structural phases with specific modulations.

Observation of stripe patterns along particular crystallographic directions.

Evidence of nano-scale phase separation affecting superconducting properties.

Abstract

Structural investigations on the K0.8Fe1.6+xSe2 superconducting materials have revealed remarkable micro-stripes arising evidently from the phase separation. Two coexisted structural phases can be characterized by modulations of q1 = 1/5[a*+3b*], the antiferromagnetic phase K0.8Fe1.6Se2, and q2 = 1/2[a*+b*], the superconducting phase K0.75Fe2Se2, respectively. These stripe patterns likely result from the anisotropic assembly of superconducting particles along the [110] and [1-10] direction. In addition to the notable stripe structures, a nano-scale phase separation also appears in present superconducting system as clearly observed by high-resolution transmission electron microscopy. Certain notable experimental data obtained in this heterogenous system can be quantitatively explained by the percolation scenario.