Figure 4. Reversible superconductor-to-insulator transition of LiTi₂O₄ films induced by Li-ion electrochemical reactions.

(a) The black, red, and blue markers indicate temperature-dependent resistivity for initial, intercalated (1st), and deintercalated (1st) LiTi₂O₄ films, respectively. The inset shows the magnified curves near T_C (normalized by the values at 15 K). Note that the initial and the deintercalated curves are overlapped to each other. (b) Passage of T_C against the number of repeats of Li-ion electrochemical reactions. The initial data is set at 0. For convenience, T_C of 0 K for all the Li-ion intercalated films represents the fact that resistivity did not fall to zero above 2 K.