Discovery of mesoscopic nematicity wave in iron-based superconductors

• Published in: Science (American Association for the Advancement of Science) Vol. 373; no. 6559; pp. 1122 - 1125
• Main Authors: Shimojima, T., Motoyui, Y., Taniuchi, T., Bareille, C., Onari, S., Kontani, H., Nakajima, M., Kasahara, S., Shibauchi, T., Matsuda, Y., Shin, S.
• Format: Journal Article
• Language: English
• Published: United States The American Association for the Advancement of Science 03.09.2021
• Subjects: Antiferromagnetism; Dichroism; Domain walls; High temperature; High temperature superconductors; Iron; Lasers; Linear dichroism; Low temperature; Order parameters; Photoelectric emission; Sine waves; Superconductivity; Unit cell; Wavelengths
• ISSN: 0036-8075; 1095-9203; 1095-9203
• DOI: 10.1126/science.abd6701

Electrons in solids can break rotational symmetry, resulting in electronic nematicity. This phenomenon has been observed in both cuprate-based and iron-based high-temperature superconductors, and its relationship to superconductivity remains a subject of debate. Shimojima et al . used linear dichroism measurements to image nematicity in two iron-based superconductors. Unexpectedly, the researchers found periodic patterns with very long wavelengths. The findings could be described with a phenomenological model assuming a train of nematic domain walls. —JS Linear dichroism measurements show periodic patterns with very long wavelengths. Nematicity is ubiquitous in the electronic phases of iron-based superconductors. The order parameter that characterizes the nematic phase has been investigated in momentum space, but its real-space arrangement remains largely unexplored. We use linear dichroism (LD) in a low-temperature laser–photoemission electron microscope to map out the nematic order parameter of nonmagentic FeSe and antiferromagnetic BaFe 2 (As 0.87 P 0.13 ) 2 . In contrast to structural domains, which have atomic-scale domain walls, the LD patterns in both materials show peculiar sinusoidal waves of electronic nematicity with wavelengths more than 1000 times as long as the unit cell. Our findings put strong constraints on the theoretical investigation of electronic nematicity.