Superconductivity in FeTe_1−xS_x Induced by Electrochemical Reaction Using Ionic Liquid Solution

Abstract

Superconductivity in FeTe 0.8 S 0.2 is successfully induced by an electrochemical reaction using an ionic liquid solution. A clear correlation between the Fe concentration in the solution and superconductivity was confirmed, suggesting that superconductivity is induced by the deintercalation of excess Fe.

Application of electrochemical method to microfabricated region in single-crystal device of FeSe1− x Te x superconductors

“…Next, we investigated the resistivity of FeSe 0.2 Te 0.8 immersed in the ionic liquid at 80 °C with no voltage application. In contrast to previous reports on FeS 0.2 Te 0.8 , 7,8) we found that T onset c for the sample KE33 (L = 60 µm, W = 100 µm, without FIB etching) is enhanced by roughly ∼0.5 K after long soaking for 360 min, as shown in Fig. 3.…”

“…The tunability of superconducting properties is crucially important. In this regard, an electrochemical method is very attractive, because it can be used to deintercalate interstitial Fe, 7,8) intercalate the spacer layers, 3) etch a surface chemically, and form a field-effect transistor (FET) utilizing the EDL structure. 4) However, this method has been applied to only polycrystalline powders and thin films, since the moving distance of ions in solids during electrochemical reactions is very short, thus requiring a large surface area per unit volume to obtain a sufficient degree of change.…”

“…9) The electrochemical reaction method was performed by a standard three-electrode method. 7,8) A Ag plate and a Pt mesh were used as the reference and counter electrodes, respectively, while an FeSe 1−x Te x sample was used as the working electrode. We used the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate (BMITFB) as the electrolyte, which was kept at 80 °C during electrochemical reactions.…”

“…Note that, in this work, we systematically changed the time interval rather than the applied voltage during electrochemical reactions, in contrast to previous studies. 7,8) The chemical degradation of FeSe 1−x -Te x samples was checked by monitoring the current between the working and counter electrodes and optical microscopy images of the sample.…”

Review of annealing effects and superconductivity in Fe1+y Te1−x Se x superconductors

“…The acid and alcoholic beverage effects were further improved to become a more controllable electrochemical reaction method performed by a standard three-electrode method [55,56]. A Ag plate and a Pt mesh were used as the reference and counter electrodes, respectively, while an FeTe 1−x S x sample was used as the working electrode.…”