Optical Study of the Free Carrier Response of LaTiO3/SrTiO3 Superlattices

TL;DR

This study uses infrared spectroscopic ellipsometry to analyze the electronic properties of LaTiO3/SrTiO3 superlattices, revealing a consistent metallic response and interface electron leakage, with temperature-dependent carrier behavior.

Contribution

It provides new insights into the free carrier response and interface electron leakage in LaTiO3/SrTiO3 superlattices using infrared spectroscopy.

Findings

Superlattices exhibit a Drude metallic response regardless of periodicity.

Sheet carrier density per interface is approximately 3x10^14 cm^-2.

Carrier relaxation time is about 35 fs at 10 K, with temperature-dependent carrier density.

Abstract

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 ~3x10^14 cm^-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 ~ 35 fs and mobility ~ 35 cm^2V^-1s^-1 at 10 K, and an unusual temperature dependence of carrier density that was attributed to the dielectric screening of quantum paraelectric SrTiO3.