Possible Liquid-Nitrogen-Temperature Superconductivity Driven by Perpendicular Electric Field in the Single-Bilayer Film of La$_3$Ni$_2$O$_7$ at Ambient Pressure

TL;DR

Applying a perpendicular electric field to La$_3$Ni$_2$O$_7$ bilayer films at ambient pressure can significantly increase the critical temperature, potentially reaching liquid nitrogen temperatures for high-temperature superconductivity.

Contribution

This work proposes and numerically verifies that a perpendicular electric field can induce high-temperature superconductivity in La$_3$Ni$_2$O$_7$ bilayers at ambient pressure, a novel approach to enhance $T_c$.

Findings

Electric field enhances $T_c$ in La$_3$Ni$_2$O$_7$ bilayers.

A voltage of 0.1-0.2 V can induce liquid-nitrogen-temperature superconductivity.

Intralayer $d$-wave pairing is strongly enhanced under electric field.

Abstract

Recently, high-temperature superconductivity (HTSC) is found in the La$_3$Ni$_2$O$_7$/SrLaAlO$_4$ ultrathin film with critical temperature $T_c$ above the McMillan limit at ambient pressure (AP). It is eager to enhance $T_c$ of La$_3$Ni$_2$O$_7$ at AP. We propose that a perpendicular electric field strongly enhances $T_c$ in the single-bilayer film of La$_3$Ni$_2$O$_7$ at AP. Under electric field, the layer with lower potential energy will accept electrons flowing from the other layer to fill in the Ni-$3d_{x^2-y^2}$ orbitals, as the nearly half-filled Ni-$3d_{z^2}$ orbital cannot accommodate more electrons. With the enhancement of the filling fraction in the $3d_{x^2-y^2}$ orbitals in this layer, the interlayer $s$-wave pairing is suppressed, but the intralayer $d$-wave pairing in this layer is strongly enhanced. We numerically verify this idea and yield that an imposed voltage of about $0.1\sim0.2$ volt between layers is enough to realize liquid-nitrogen-temperature HTSC in this single bilayer at AP. Our results appeal for experimental verification.