Dr. Lucia Steinke

National High Magnetic Field Laboratory High B/T Facility

University of Florida

Host: Gannon

Title: Towards a universal measurement platform for calorimetric and thermal transport measurements at the combined extremes of high magnetic fields and sub-millikelvin temperatures

Abstract: The NHMFL High B/T facility at the University of Florida in Gainesville pursues the mission to enable user experiments at the combined extremes of high magnetic fields B and ultra-low temperatures (ULT) below one millikelvin. While almost all measurement techniques like electrical transport or magnetometry require adaptations to be successfully performed in this environment, calorimetry and thermal transport are particularly challenging due to a lack of suitable thermometry. Existing thermometers typically either lack ULT sensitivity, are incompatible with high magnetic fields, or have too high masses and long thermalization times to allow for measurements of small samples. Specific heat and thermal transport experiments at ULT and high B - especially on small crystals - would be essential to studies of quantum criticality, superconductors with very low transition temperatures, or to provide evidence for a quantum spin liquid state. To meet increased user demand for such experiments, our group is developing fast and compact ULT thermometers to form the basis of a universal measurement platform for calorimetry and thermal transport of a variety of samples. The measurement principle relies on the well-established temperature dependent viscosity of liquid ³He that is probed by tracking the resonance of quartz tuning forks immersed in the liquid. I will report on recent progress in the miniaturization of such tuning fork thermometers (TFT), and present results from field and temperature dependent performance tests. 

The National High Magnetic Field Laboratory is supported by the National Science Foundation through NSF DMR-1644779 and the State of Florida.