# Sixfold enhancement of superconductivity in a tunable electronic nematic system

## TL;DR

This study demonstrates that strong nematic fluctuations near a quantum phase transition can significantly enhance superconductivity, achieving a sixfold increase in transition temperature in a tunable, non-magnetic electronic nematic system.

## Contribution

It provides direct evidence linking nematic fluctuations to superconductivity enhancement, using elastoresistance measurements in a model system without magnetic order.

## Key findings

- Sixfold increase in superconducting transition temperature.
- Nematic fluctuations are directly correlated with pairing strength.
- Suppression of nematic order at quantum critical point enhances superconductivity.

## Abstract

The electronic nematic phase, wherein electronic degrees of freedom lower the crystal rotational symmetry, is a common motif across a number of high-temperature superconductors. However, understanding the role and influence of nematicity and nematic fluctuations in Cooper pairing is often complicated by the coexistence of other orders, particularly long-range magnetic order. Here we report the enhancement of superconductivity in a model electronic nematic system absent of magnetism, and show that the enhancement is directly born out of strong nematic fluctuations emanating from a tuned quantum phase transition. We use elastoresistance measurements of the Ba$_{1-x}$Sr$_{x}$Ni$_2$As$_2$ substitution series to show that strontium substitution promotes an electronically driven $B_{1g}$ nematic order in this system, and that the complete suppression of that order to absolute zero temperature evokes a dramatic enhancement of the pairing strength, as evidenced by a sixfold increase in the superconducting transition temperature. The direct relation between enhanced pairing and nematic fluctuations in this model system, as well as the interplay with a unidirectional charge density wave order comparable to that found in the cuprates, offers a means to elucidate the role of nematicity in boosting superconductivity.