# Tuning the superconducting transition of SrTiO$_3$-based 2DEGs with light

## TL;DR

This study demonstrates that visible light irradiation at ultra low temperatures can nonvolatily tune the resistance and superconducting transition temperature of SrTiO$_3$-based 2DEGs, offering a new control method for these quantum systems.

## Contribution

It introduces a novel light-based, nonvolatile method to tune the superconducting properties of SrTiO$_3$-based interfaces at ultra low temperatures.

## Key findings

- Resistance decreases by a factor of five upon irradiation.
- Superconducting transition temperature $T_c$ shifts downward with resistance.
- The resistance and $T_c$ can be reverted by heating above 10 K.

## Abstract

The resistivity of the two dimensional electron gas that forms at the interface of strontium titanate with various oxides is sensitive to irradiation with visible light. In this letter we present data on the interface between the band gap insulators LaAlO$_3$ (LAO) and SrTiO$_3$ (STO). We operate a light emitting diode at temperatures below 1 K and utilize it to irradiate the LAO/STO interface at ultra low temperatures. On irradiation the resistance of this system is lowered continuously by a factor of five and the resistance change is persistent at low temperatures as long as the sample is kept in the dark. This makes a characterization of transport properties in different resistive states over extended time periods possible. Our pristine sample gets superconducting below 265 mK. The transition temperature $T_c$ shifts downwards on the persistent photo-induced lowering of the resistance. The persistent photoconductance can be completely reverted by heating the structure above 10 K in which case $T_c$ as well takes on its original value. Thus very similar to field effect control of electron densities irradiation at low temperatures offers a versatile tuning knob for the superconducting state of STO-based interfaces which in addition has the advantage to be nonvolatile.