Measuring station "strain" in a high-field helium cryostat

• Subject Area: Condensed Matter Physics
• Term: Funded in 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 468546864

We apply for a measurement station „strain“ that consists of a high-field Helium-cryostat, measurementcell and electronics. The station will enable measurements on diverse materials in a broad andcryogenic temperature environment (1.8K-ca.400K) and in high magnetic fields up to 17T – an environmentthat is decisive to access the unique properties of quantum materials. Strain is a thermodynamicquantity that encodes a variety of interesting and unique properties of a material. By determiningthese quantities in an advanced sample environment, we will achieve decisive contributionsto different projects in the area of quantum materials.The effect of large uniaxial strain on the Co-based antiferromagnets (Sr1-xCax)Co2As2 will be studied.This material exhibits complex magnetism and it is expected that the external strain will case switchingbetween different types of magnetic order. The external symmetry breaking may even inducenew phases that are otherwise not stable. In addition, strain may give access to critical behavior andthus act as a unique “tuning parameter”. Accurate determination of thermal strain (i.e., thermal expansivity)and magnetostriction will complete the project.Furthermore, we will study the strain behavior (thermal expansivity, magnetostriction, elastic moduli,influence of external uniaxial strain) of Fe(Se,S) in proximity to its nematic quantum critical point.Fe(Se,S) has by now the role of a model system for the still-enigmatic nematic phase. Although nematicorder is intrinsically linked to anisotropic strain, little is known about the strain behavior ofFe(Se,S) at low temperature and in high magnetic fields. Our measurements will thus make an importantcontribution to clarify the behavior of superconductivity arising around a nematic quantumcritical point.In addition, we will study the strain behavior of the family of van-der-Waals ferromagnets FeNGeTe2(N=3,4,5) and of the nematic insulator KFe0.8Ag1.2X2, (X=S,Se,Te)].

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Messplatz "Dehnung" im Hochfeld-Heliumkryostaten
• Instrumentation Group: 0120 Supraleitende Labormagnete
• Applicant Institution: Ruhr-Universität Bochum
• Leader: Professorin Dr. Anna E. Böhmer