Observation of transient superconductivity at LaAlO$_3$/SrTiO$_3$ interface

We present observations of a novel magnetic field assisted transient superconducting state in the two-dimensional electron gas existing at the interface of LaAlO$_3$/SrTiO$_3$ heterostructure. The observed transient superconductivity appears upon the application of a time dependent magnetic field at a temperature significantly higher than the normal superconducting T$_C$ reported previously in this material. This metastable state depends critically on the doping density in the parent compound. It appears concomitantly with a Lifshitz transition because of the interplay between ferromagnetism and superconductivity and the finite relaxation time of the in-plane magnetization. Superconductivity and magnetism are antagonistic to each other. Hence the observation of the co-existence of these two phases in the oxide heterostructures has thrown up many interesting and yet unanswered questions. Our results clearly demonstrate the inherently metastable nature of the superconducting state competing with a magnetic order in these systems. An open question in this field is the energetics of the interplay between these two competing orders and the present observation goes a long way in understanding the underlying mechanism.