Ionic liquid gating of YBa₂Cu₃O_7−x with a BN capping layer for enhanced stability and efficiency

In this study, we explored the impact of ionic liquid gating on YBa₂Cu₃O_7−x superconductivity. We observed that direct contact of YBa₂Cu₃O_7−x and the ionic liquid N-diethyl-N-methyl-N-(2methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide (DEME-TFSI) results in irreversible electrochemical reactions, despite the application of a relatively low gate voltage at 220 K. Capping a thin layer of boron nitride (BN) on YBa₂Cu₃O_7−x enabled a reversible modulation of carrier density at 300 K. Benefiting from the higher ion mobility of ionic liquid at 300 K, this modification led to more than a one-time increase in carrier density, a 3-time improvement in voltage modulation efficiency, and a reversible tuning of the superconducting temperature. These findings suggest that using a BN capping layer holds promise for enhancing the stability and efficiency of devices using ionic liquid gating.