# Non-Volatile Superconductivity in an Insulating Copper Oxide Induced via Ionic Liquid Gating

## TL;DR

This study demonstrates a novel ionic liquid gating technique to reversibly and permanently induce superconductivity in insulating Pr_2CuO_{4 ext{-}\delta} films, revealing new control over high-T_c cuprate states for advanced electronics.

## Contribution

It introduces a dual-mechanism ionic liquid gating method to control volatile and non-volatile superconductivity in an insulating cuprate, a first in the field.

## Key findings

- Reversible switching between superconducting and non-superconducting states via positive electric fields.
- Achieving persistent superconductivity after removing the gate voltage.
- Observation of oxygen vacancy healing as the mechanism for non-volatile superconductivity.

## Abstract

Manipulating the superconducting states of high-T_c cuprate superconductors in an efficient and reliable way is of great importance for their applications in next-generation electronics. Traditional methods are mostly based on a trial-and-error method that is difficult to implement and time consuming. Here, employing ionic liquid gating, a selective control of volatile and non-volatile superconductivity is achieved in pristine insulating Pr_2CuO_{4\pm\delta} film, based on two distinct mechanisms: 1) with positive electric fields, the film can be reversibly switched between non-superconducting and superconducting states, attributed to the carrier doping effect. 2) The film becomes more resistive by applying negative bias voltage up to -4 V, but strikingly, a non-volatile superconductivity is achieved once the gate voltage is removed. Such a persistent superconducting state represents a novel phenomenon in copper oxides, resulting from the doping healing of oxygen vacancies in copper-oxygen planes as unraveled by high-resolution scanning transmission electron microscope and in-situ x-ray diffraction experiments. The effective manipulation and mastering of volatile/non-volatile superconductivity in the same parent cuprate opens the door to more functionalities for superconducting electronics, as well as supplies flexible samples for investigating the nature of quantum phase transitions in high-T_c superconductors.

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Source: https://tomesphere.com/paper/1906.07360