Gate-tunable superconductivity in oxide heterostructures
Shamashis Sengupta (CSNSM, Université Paris-Sud)
The realization of two-dimensional electronic gases (2DEGs) in oxide-based heterostructures (e.g. LaAlO3/SrTiO3) has led to important discoveries about superconductivity in low dimensions. There have been reports of the observation of pairing interactions without superconductivity (Cheng et al., Nature 521, 196 (2015)) and density-of-states features resembling the pseudogap in cuprates (Richter et al., Nature 502, 528 (2013)). Consequently, this 2DEG has emerged as a model system to study the physics of Cooper pair formation in two dimensions and to gain useful insights about complex problems, e.g., the phase diagram of high temperature superconductors. In this talk, we will discuss about a new method developed in our group for realizing such superconducting systems in oxide heterostructures, and the results of experiments to characterize their properties. Due to the low carrier density, it is possible to change it using a gate voltage following the principle of a field-effect transistor. The superconducting critical parameters (temperature and field) are tunable as a function of the gate voltage, leading to a ‘superconducting dome’ in the phase diagram. The possibility of continuously varying the carrier density allows us to study different equilibrium and non-equilibrium features characterizing the electronic phases. Results of some recent experiments will be presented.