Specific Heat Study of the BiS2-Based Superconductor

摘要

There have been a few reports on specific heat measurements in BiS2-based superconductors. Electronic specific heat coefficient gamma and Debye temperature Theta(D) are not obtained accurately from specific heat measurements, because the measured temperature is relatively high. Furthermore, polycrystalline samples show a distinct upturn in C-P/T below 2.0 K; superconducting (SC) gap symmetry cannot be discussed. It is highly desirable to measure the heat capacity using a single crystal to reveal the SC state. This review article summarizes studies on specific heat of the BiS2-based superconductors. Particularly, the constructional details of our sensitive calorimeter designed for the BiS2-based superconductors with very small heat capacity are reviewed. The addendum value reaches approximately 0.8 nJ/K-2 at 1 K, which enables the measurement of the heat capacity of the small single crystal (similar to 1 mg) of the BiS2-based superconductors. The SC-gap symmetry of LaO0.5F0.5BiSSe is elucidated through specific heat measurements using our homemade calorimeter.