Superconductivity induced by doping holes in the nodal-line semimetal NaAlGe

TL;DR

This study demonstrates that hole doping in NaAlGe suppresses its pseudogap and induces superconductivity, revealing a link between excitonic fluctuations and superconducting behavior in this nodal-line semimetal.

Contribution

It provides the first evidence that doping holes in NaAlGe can induce superconductivity by suppressing the pseudogap, highlighting excitonic fluctuations as a potential mechanism.

Findings

Pseudogap decreases with increasing Zn doping.

Superconducting dome appears with T_c up to 2.8 K.

Superconductivity likely driven by excitonic fluctuations.

Abstract

The nodal-line semimetals NaAlSi and NaAlGe have significantly different ground states despite having similar electronic structures: NaAlSi exhibits superconductivity below 7 K, while NaAlGe exhibits semiconductive electrical conductivity at low temperatures, indicating the formation of a pseudogap at approximately 100 K. The origin of the pseudogap in NaAlGe is unknown but may be associated with excitonic instability. We investigated hole-doping effects on the ground state in the solid solution Na(Al1-xZnx)Ge and discovered that the pseudogap is suppressed continuously with increasing Zn content, followed by the appearance of a superconducting dome with the highest transition temperature of 2.8 K. This superconductivity most likely results from excitonic fluctuations.