Microscopic co-existence of superconductivity and magnetism in Ba1-xKxFe2As2

TL;DR

This study demonstrates that in underdoped Ba1-xKxFe2As2, superconductivity and magnetism coexist microscopically rather than phase-separately, challenging previous beliefs about their relationship.

Contribution

The paper provides evidence of microscopic coexistence of magnetism and superconductivity in hole-doped Ba1-xKxFe2As2, contradicting the common phase separation paradigm.

Findings

Microscopic coexistence of magnetism and superconductivity in underdoped Ba1-xKxFe2As2

Reduction of magnetic moment below superconducting transition

Decrease in orthorhombic lattice distortion below Tc

Abstract

It is widely believed that, in contrast to its electron doped counterparts, the hole doped compound Ba1-xKxFe2As2 exhibits a mesoscopic phase separation of magnetism and superconductivity in the underdoped region of the phase diagram. Here, we report a combined high-resolution x-ray powder diffraction and volume sensitive muon spin rotation study of underdoped Ba1-xKxFe2As2 (0 \leq x \leq 0.25) showing that this paradigm is wrong. Instead we find a microscopic coexistence of the two forms of order. A competition of magnetism and superconductivity is evident from a significant reduction of the magnetic moment and a concomitant decrease of the magneto-elastically coupled orthorhombic lattice distortion below the superconducting phase transition.