Quantum Phase Transitions and Superconductivity in Calcium Doped Strontium Titanate

Abstract

Strontium titanate (SrTiO3) is a quantum paraelectric, an insulating dielectric material that approaches a state of ferroelectricity, but never achieves it as its temperature approaches absolute zero. Recent research suggests however, that in a field effect transistor (FET) geometry charge may be induced into SrTiO3, and metallic properties and superconductivity can be achieved at temperatures slightly above absolute zero. We have procured single crystals of calcium doped strontium titanate (Sr1-xCaxTiO3) with a calcium concentration of x=0.06. This material actually undergoes a transition to ferroelectricity at temperatures substantially above absolute zero. We plan to measure its dielectric constant as a function of temperature. If the result of this measurement indicates that a sharp enough ferroelectric transition occurs, then we will test the material in a FET geometry and attempt to induce metallic properties in Sr1-xCaxTiO3. If this is found to be possible, the next step would be to try to search for superconductivity.