Superconductivity in quasi-one-dimensional K$_2$Cr$_3$As$_3$ with significant electron correlations

TL;DR

This paper reports the discovery of bulk superconductivity at 6.1 K in a quasi-one-dimensional chromium pnictide with strong electron correlations, exhibiting unconventional features and potential non-Fermi liquid behavior.

Contribution

It presents the first observation of superconductivity in K$_2$Cr$_3$As$_3$, highlighting its quasi-one-dimensional structure and strong electron correlations as key factors.

Findings

Superconductivity at 6.1 K in K$_2$Cr$_3$As$_3$

Large electronic specific-heat coefficient indicating strong correlations

Upper critical field exceeds Pauli limit, suggesting unconventional superconductivity

Abstract

We report the discovery of bulk superconductivity (SC) at 6.1 K in a quasi-one-dimensional (Q1D) chromium pnictide K$_2$Cr$_3$As$_3$ which contains [(Cr$_3$As$_3$)$^{2-}$]$_{\infty}$ double-walled subnano-tubes with face-sharing Cr$_{6/2}$ (As$_{6/2}$) octahedron linear chains in the inner (outer) wall. The material has a large electronic specific-heat coefficient of 70$\sim$75 mJ K$^{-2}$ mol$^{-1}$, indicating significantly strong electron correlations. Signature of non-Fermi liquid behavior is shown by the linear temperature dependence of resistivity in a broad temperature range from 7 to 300 K. Unconventional SC is preliminarily manifested by the estimated upper critical field exceeding the Pauli limit by a factor of three to four. The title compound represents a rare example that possibly unconventional SC emerges in a Q1D system with strong electron correlations.