Microwave flux-flow Hall effect of superconductors: (1) Method

The bound states in the vortex core of superconductors can be classified in terms of the cleanness of the vortex core. High T_c cuprate superconductors are expected to be in the clean limit because of the large superconducting gap. However, previous measurements of the effective viscous drag coefficient, η^*, for wide range of cleanness found that the vortex cores of high T_c cuprates were in the moderately clean limit, as a universal trend [1]. These results may suggest that there exists an extra dissipation mechanism due to the vortex motion which have not been considered so far. However, η^* is the mixture of the longitudinal viscous drag coefficient and the Hall coefficient [2]. Thus, η^* measurement may not reflect the true electronic states in the vortex core. Therefore, it is necessary to directly measure the flux flow Hall effect and to evaluate the true core states. In order to neglect pinning, we need high frequencies. Thus, we developed a new method for microwave Hall effect measurement using a cross shaped bimodal cavity. In this talk, we will show the detail of the measurement and the analysis. We applied our system to Bi, and obtained a good result.
[1] e.g., Y. Tsuchiya, et al., Phys. Rev. B 63 184517 (2001).
[2] G. Blatter, et.al., Rev. Mod. Phys. 66, 1125 (1994).