Oxygen vacancy clustering and pseudogap behaviour at the LaAlO₃/SrTiO₃ interface.

The two-dimensional electron gas at the LaAlO3/SrTiO3 interface promises to add a new dimension to emerging electronic devices due to its high degree of tunability. Defects in the form of oxygen vacancies in titanate surfaces and interfaces, on the other hand, play a key role in the emergence of the ordered states and their tunability at the interface. On the basis of an effective model, we study the influence of oxygen vacancies on the superconductivity and ferromagnetism at the LaAlO3/SrTiO3 interface. Using the Bogoliubov-de Gennes formulation in conjunction with Monte Carlo simulation, we find a clustering of the oxygen vacancies at the interface that favours the formation of coexisting ferromagnetic puddles spatially separated from the superconductivity. We also find a carrier freeze-out at low temperatures, observed experimentally in a wide variety of samples. A sufficiently large amount of oxygen vacancies leads to pseudogap-like behaviour in the superconducting state.