A comparative study of superconductivity at LaAlO3/SrTiO3 and BaTiO3/LaAlO3/SrTiO3 heterointerfaces

Lead-free BaTiO3 (BTO) film was fabricated by pulsed laser deposition on LaAlO3/SrTiO3 (LAO/STO) heterostructure in oxygen pressure of 2 x 10(-3) Pa, which is experimentally required for ensuring the two-dimensional electron gas at LAO/STO heterointerface. Modulation of back-gate voltage on the superconductivity of LAO/STO and BTO/LAO/STO heterointerfaces was studied. The results indicate that the back-gate voltage can adjust the resistance at high temperatures around 300 mK, while it does not modulate the superconducting transition temperature of LAO/STO, which occurs at 160 mK. As for BTO/LAO/STO, it still shows a superconducting transition-like behavior at 110 mK. However, when a negative back-gate voltage is applied, the superconducting transition-like behavior disappears, and after removing the voltage, unlike what was observed for LAO/STO, the superconductivity cannot be recovered. Given this, some underlying mechanisms are proposed.