Ferroelectric quantum criticality and enhanced superconductivity in plastically deformed strontium titanate

TL;DR

This study demonstrates that plastic deformation in strontium titanate induces low-dimensional superconductivity and quantum-critical ferroelectric fluctuations, significantly enhancing $T_c$ and revealing a new method to manipulate quantum material properties.

Contribution

It introduces plastic deformation as a novel approach to induce and control superconductivity and ferroelectric quantum criticality in SrTiO$_3$, linking dislocation structures to electronic enhancements.

Findings

Plastic deformation induces superconductivity above the original $T_c$.

Dislocation structures correlate with enhanced superconductivity.

Deformation induces ferroelectric fluctuations and inhomogeneous order.

Abstract

The properties of quantum materials are commonly tuned using experimental variables such as pressure, magnetic field and doping. Here we explore a different approach: irreversible, plastic deformation of single crystals. We show for the superconductor SrTiO$_3$ that compressive plastic deformation induces low-dimensional superconductivity significantly above the superconducting transition temperature ($T_c$) of undeformed samples, with evidence of superconducting correlations at temperatures two orders of magnitude above the bulk $T_c$. The superconductivity enhancement is correlated with the appearance of self-organized dislocation structures, as revealed by diffuse neutron and X-ray scattering. We also observe signatures of deformation-induced quantum-critical ferroelectric fluctuations and inhomogeneous ferroelectric order via Raman scattering. These results suggest that the strain surrounding the self-organized dislocation structures induces local ferroelectricity and quantum-critical dynamics that strongly influence $T_c$, consistent with a theory of superconductivity enhanced by soft polar fluctuations. More broadly, our results demonstrate the promise of plastic deformation and dislocation engineering as tools to manipulate electronic properties of quantum materials.