Magnetic field tuned superconductor-to-insulator transition at the LaAlO$_3$ /SrTiO$_3$ interface

Abstract

We present a study of the magnetic field tuned superconductor-to-insulator transition (SIT) in the electron gas that forms at the LaAlO$_3$/SrTiO$_3$ interface. We find that the magnetic field induces a transition into a weakly insulating state, as is observed for the electrostatically tuned SIT at this interface. Finite size scaling of the magnetoresistance yields the critical exponent product $z\nu \simeq$ 7/3, indicating that the transition is governed by quantum percolation effects. While such critical exponents have been reported previously for high resistance films, they have not been reported for a low resistance system like ours, with a maximum sheet resistance of $\approx$ 1.5 k$\Omega$, much less than the quantum of resistance $R_Q \equiv h/4e^2 = 6.45$ k$\Omega$.