Optical study of the free-carrier response of LaTiO3/SrTiO3 superlattices

We used infrared spectroscopic ellipsometry to investigate the electronic properties of LaTiO3/SrTiO3 superlattices (SLs). Our results indicated that, independent of the SL periodicity and individual layer thickness, the SLs exhibited a Drude metallic response with sheet carrier density per interface ≈3×1014cm-2. This is probably due to the leakage of d electrons at interfaces from the Mott insulator LaTiO3 to the band insulator SrTiO3. We observed a carrier relaxation time ≈35fs and mobility ≈35cm2V-1s-1 at 10 K, and an unusual temperature dependence of carrier density that was attributed to the dielectric screening of quantum paraelectric SrTiO3.