Imaging Nematic Transitions in Iron-Pnictide Superconductors with a Quantum Gas

TL;DR

This paper demonstrates the use of a novel quantum sensing microscope to simultaneously image and analyze nematic phase transitions in iron-pnictide superconductors, revealing concurrent transport and structural changes.

Contribution

It introduces a multimodal imaging approach combining SQCRAMscope with optical birefringence measurements to study nematicity in quantum materials.

Findings

First local measurement of resistivity anisotropy in iron pnictides.

Observation of sharp, nearly concurrent structural and transport transitions.

Demonstration of SQCRAMscope's capability for complex quantum material analysis.

Abstract

The SQCRAMscope is a recently realized Scanning Quantum CRyogenic Atom Microscope that utilizes an atomic Bose-Einstein condensate to measure magnetic fields emanating from solid-state samples. The quantum sensor does so with unprecedented DC sensitivity at micron resolution from room-to-cryogenic temperatures. An additional advantage of the SQCRAMscope is the preservation of optical access to the sample: Magnetometry imaging of, e.g., electron transport may be performed in concert with other imaging techniques. This multimodal imaging capability can be brought to bear with great effect in the study of nematicity in iron-pnictide high-temperature superconductors, where the relationship between electronic and structural symmetry-breaking resulting in a nematic phase is under debate. Here, we combine the SQCRAMscope with an in situ microscope that measures optical birefringence near the surface. This enables simultaneous and spatially resolved detection of both bulk and near-surface manifestations of nematicity via transport and structural deformation channels, respectively. By performing the first local measurement of emergent resistivity anisotropy in iron pnictides, we observe sharp, nearly concurrent transport and structural transitions. More broadly, these measurements demonstrate the SQCRAMscope's ability to reveal important insights into the physics of complex quantum materials.