Electric-field-effect modulation of the transition temperature, mobile carrier density, and in-plane penetration depth of NdBa2Cu3O7-δ thin films

We explore the relationship between the critical temperature T-c, the mobile areal carrier density n(2D), and the zero-temperature magnetic in-plane penetration depth lambda(ab)(0) in very thin underdoped NdBa2Cu3O7-delta films near the superconductor to insulator transition using the electric-field-effect technique. Having established consistency with a Kosterlitz-Thouless transition, we observe that T-KT depends linearly on n(2D), the signature of a quantum superconductor to insulator transition in two dimensions with z (v) over bar = 1, where z is the dynamic and (v) over bar is the critical exponent of the in-plane correlation length.