[7p-S42-1~16] 11.1 Fundamental properties

[7p-S42-10] Improvement of Superconducting Properties in Single Crystalline FeSe_1-xTe_x Device by Applying Electrochemical Methods to Microfabricated Structure

Kazuhiro Okada¹, Tomohiro Takagi¹, Masahiro Kobayashi¹, Haruka Ohnuma¹, Takashi Noji², Yoji Koike², Shin-ya Ayukawa³, 〇Haruhisa Kitano¹ (1.Aoyama Gakuin Univ., 2.Tohoku Univ., 3.Okayama Univ.)

Keywords:Fe-based superconductors, electrochemical method, microfabrication

Iron chalcogenide FeCh (Ch=S, Se, Te) superconductors have the simplest crystal structure among Fe-based superconductors and show several exotic properties such as a large enhancement of the superconducting transition temperature T_c by the electric field effect to thin films and a large superconducting fluctuation induced by a proximity to BCS-BEC crossover. However, the superconductivity and magnetism in this material are strongly affected by Fe non-stoichiometry, originating in the partial occupation of excess Fe at the interstitial site in Te/Se layers. In order to reduce this effect, oxygen annealing and electrochemical methods are often needed. In this talk, we present an experimental study on the application of electrochemical method to the microfabricated structure in single crystalline FeSe_0.2Te_0.8 devices. We succeeded in increasing T_c and decreasing the residual resistance across the small bridge of FeSe_0.2Te_0.8 device by making the electrochemical reaction in only a few minutes. This strongly suggests that the application of electrochemical method to the microfabricated structure in single crystalline superconductors is quite useful to enhance and control the performance of the superconducting junction devices made of Fe-based superconductors.