Gate induced metallicity and absence of superconductivity in BSTO/LCO heterostructure

Abstract

We fabricated Ba_0.8Sr_0.2TiO${}_3$ (BSTO)/La${}_2$CuO${}_4$ (LCO) heterostructure on SrTiO${}_3$ (STO) substrate and investigated its structure and physical properties. X-ray diffraction and reciprocal space mapping confirm the epitaxial growth of BSTO/LCO/STO heterostructure. X-ray photoelectron spectroscopy and UV–Visible spectroscopy measurements reveal a straddling band alignment of the BSTO/LCO heterojunction. Such band alignment facilitates the accumulation of both electrons and holes at the interface. Their movement depends on the direction of the internal field of the BSTO film. Electrical transport measurements have revealed a signature of insulator-to-metal transition (IMT) in response to applied gate voltages $\pm V_g$. Hall measurements confirm the presence of electron and hole type charge carriers under ＋V${}_g$ and −V${}_g$, respectively. We have proposed a screening mechanism linked to the polarization state of the BSTO film to explain the observed IMT.