Tartaric acid in red wine as one of the key factors to induce superconductivity in FeTe0.8S0.2

► We investigated the red wine dependence of the shielding volume fraction in FeTe0.8S0.2. ► The tartaric acid is correlated with the superconductivity in FeTe0.8S0.2. ► Our results suggest the tartaric acid is one of the key factors to induce superconductivity in FeTe0.8S0.2. We investigated the key factor of superconductivity in FeTe1−xSx induced by alcoholic beverages. To understand the reason why red wine shows larger shielding volume fraction than the other alcoholic beverages, the red wine dependence of superconductivity was performed. All the samples heated in red wine made from different grapes shows large shielding volume fraction compared with the samples heated in water and other alcoholic beverages. The shielding volume fraction of the red wine samples is proportional to the concentration of tartaric acid. We found that tartaric acid is one of the key factors to induce superconductivity in FeTe1−xSx.