Electrostatic Control of the Evolution from Superconductor to Insulator in Ultrathin Films of Yttrium Barium Copper Oxide

摘要

The electrical transport properties of ultrathin YBCO films have beenmodified using an electric double layer transistor configuration employing anionic liquid. The films were grown on SrTiO3 substrates using high pressureoxygen sputtering. A clear evolution from superconductor to insulator wasobserved in nominally 7 unit cell thick films. Using a finite size scalinganalysis, curves of resistance versus temperature, R(T), over the temperaturerange from 6K to 22K were found to collapse onto a single scaling function,which suggests the the presence of a quantum critical point. However thescaling failed at the lowest temperatures suggesting the presence of anadditional phase between the superconducting and insulating regimes.