Inferior interfacial superconductivity in 1 UC FeSe/SrVO$_3$/SrTiO$_3$ with screened interfacial electron-phonon coupling

TL;DR

This study investigates a new monolayer FeSe/SrVO$_3$/SrTiO$_3$ interface where electron screening reduces interfacial electron-phonon coupling, revealing its role in superconductivity enhancement and disentangling it from dimensionality effects.

Contribution

It introduces a novel FeSe/SrVO$_3$/SrTiO$_3$ interface with screened interfacial EPC, providing insights into the mechanisms of superconductivity enhancement.

Findings

Screened interfacial EPC reduces pairing temperature compared to other FeSe/oxide interfaces.

Despite similar doping, the FeSe/SrVO$_3$ interface exhibits lower $T_g$ than FeSe/SrTiO$_3$.

Disentangling EPC effects from dimensionality clarifies their roles in $T_g$ enhancement.

Abstract

Monolayer FeSe/TiO$_x$ and FeSe/FeO$_x$ interfaces exhibit significant superconductivity enhancement compared to bulk FeSe, with interfacial electron-phonon coupling (EPC) playing a crucial role. However, the reduced dimensionality in monolayer FeSe, which may drive superconducting fluctuations, complicates the understanding of the enhancement mechanisms. Here we construct a new superconducting interface: monolayer FeSe/SrVO$_3$/SrTiO$_3$, in which the itinerant electrons of highly metallic SrVO$_3$ films can screen all the high-energy Fuchs-Kliewer phonons, including those of SrTiO$_3$, making it the first FeSe/oxide system with screened interfacial EPC while maintaining the monolayer FeSe thickness. Despite comparable doping levels, the heavily electron-doped monolayer FeSe/SrVO$_3$ exhibits a lower pairing temperature ($T_\mathrm{g}$ $\sim$ 48 K) than FeSe/SrTiO$_3$ and FeSe/LaFeO$_3$. Our findings disentangle the contributions of interfacial EPC from dimensionality on enhancing $T_\mathrm{g}$ in FeSe/oxide interfaces, underscoring the importance of interfacial EPC in $T_\mathrm{g}$ enhancement. This FeSe/VO$_x$ interface also provides a platform for studying the interfacial superconductivity.