Electric-Field Induced Superconductor-Insulator Transitions in Exfoliated Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ Flakes

TL;DR

This study demonstrates a reversible superconductor-insulator transition in exfoliated BSCCO flakes induced by electric field gating, revealing insights into the quantum phase transition and density of states evolution.

Contribution

It introduces a method to control SIT in BSCCO using solid ion conductor gating and combines it with tunneling spectroscopy to study electronic properties.

Findings

Reversible SIT achieved via lithium ion gating.

Scaling analysis confirms 2D quantum phase transition behavior.

Density of states shows V-shaped gaps and symmetric suppression in the insulating regime.

Abstract

We realize superconductor-insulator transitions (SIT) in mechanically exfoliated Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ (BSCCO) flakes and address simultaneously their transport properties as well as the evolution of density of states. Back-gating via the solid ion conductor engenders a reversible SIT in BSCCO, as lithium ions from the substrate are electrically driven into and out of BSCCO. Scaling analysis indicates that the SIT follows the theoretical description of a two-dimensional quantum phase transition (2D-QPT). We further carry out tunneling spectroscopy in graphite(G)/BSCCO heterojunctions. We observe V-shaped gaps in the critical regime of the SIT. The density of states in BSCCO gets symmetrically suppressed by further going into the insulating regime. Our technique of combining solid state gating with tunneling spectroscopy can be easily applied to the study of other two-dimensional materials.