Emergent defect states as a source of resistivity anisotropy in the nematic phase of iron pnictides

TL;DR

This paper investigates how emergent defect states caused by disorder and anisotropic spin fluctuations lead to resistivity anisotropy in the nematic phase of iron pnictides, explaining experimental observations.

Contribution

It introduces the concept of emergent defect states as a key mechanism for resistivity anisotropy in the nematic phase of Fe-based superconductors.

Findings

Emergent defect states act as anisotropic scatterers affecting conductivity.

These defect states are crucial for understanding transport anisotropy.

Theoretical calculations match experimental resistivity anisotropy data.

Abstract

We consider the role of potential scatterers in the nematic phase of Fe-based superconductors above the transition temperature to the (pi,0) magnetic state but below the orthorhombic structural transition. The anisotropic spin fluctuations in this region can be frozen by disorder, to create elongated magnetic droplets whose anisotropy grows as the magnetic transition is approached. Such states act as strong anisotropic defect potentials which scatter with much higher probability perpendicular to their length than parallel, although the actual crystal symmetry breaking is tiny. We calculate the scattering potentials, relaxation rates, and conductivity in this region, and show that such emergent defect states are essential for the transport anisotropy observed in experiments.