Cryogen-free thermodynamic and transport measurement system (low T, high B)

• Subject Area: Condensed Matter Physics
• Term: Funded in 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 530330511

We apply for a cryogen-free measurement platform for transport and thermodynamic properties at low temperatures and in high magnetic fields. The platform will be central for the newly set-up chair for experimental physics IV (experimental solid-state physics) at the Ruhr-University Bochum. We will focus on the investigation of quantum materials in a broad and cryogenic temperature range and in high magnetic fields using fundamental thermodynamic and transport methods – crucial for understanding their exotic properties. Single-crystalline samples are prepared in-house, which ensures the use of the system to full capacity. Sample environment: the cryogen-free measurement platform with He-3 option routinely provides a temperature environment of 0.4-400 K. No liquid Helium supply is necessary, which enables its continuous use – independent from the supply situation with the commodity Helium. Magnetic fields up to 14 T will enable the study of high field effects. Measured quantities: the central measured quantities for the present proposal are the electrical resistance, the specific heat capacity and the magnetization. Together with the measurement station „strain“ (currently in the built-up phase at the chair), the platform will enable the study of the majority of the thermodynamic quantities and the fundamental transport of magnetic quantum materials. Scientific questions: The measurement platform will enable numerous competitive projects. It will enable the characterization of phase transitions, of magnetic properties and of fundamental excitations at low temperatures. One important project (ERC) will focus on a variety of nematic superconductors (including Ba(Fe,Co)2As2 und SrxBi2Se3), where the characterization of their superconductivity at very low temperatures and in high magnetic fields is of central importance for this high-risk/high-gain project. Other projects are concerned with the composite collective excitations in several model systems for the coexistence of two order parameters, and with the properties of the antiferromagnet (Sr,Ca)Co2As2 in high magnetic fields and under anisotropic strain. Several projects in preparation concern the search for new materials, e.g., materials with coupled electronic-structural phase transitions and magnetic transition-metal dichalcogenides, as well as the materials research in the planned excellence cluster “Transforming Materials (Science)”. Altogether, the vast majority of the projects at the chair will profit from the measurement platform, mostly via the characterization of the single-crystal samples prepared in-house. The system will further be made available to members of other groups via a future “shared-labs” initiative of the materials research department of the Ruhr-University Bochum.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Kryogenfreie Thermodynamik- und Transport-Messplattform
• Instrumentation Group: 8550 Spezielle Kryostaten (für tiefste Temperaturen)
• Applicant Institution: Ruhr-Universität Bochum
• Leader: Professorin Dr. Anna E. Böhmer