Superconductivity in the vicinity of antiferromagnetic order in CrAs

TL;DR

CrAs exhibits unconventional superconductivity near an antiferromagnetic quantum critical point induced by high pressure, revealing a new pathway to discover novel superconductors in transition-metal systems.

Contribution

This study reports the discovery of pressure-induced superconductivity in CrAs near an antiferromagnetic order, highlighting a new system for exploring unconventional superconductivity.

Findings

Superconductivity appears at ~2 K near 8 kbar pressure.

Antiferromagnetic order is suppressed at the critical pressure.

Normal-state properties suggest proximity to a magnetic quantum critical point.

Abstract

One of the common features of unconventional, magnetically mediated superconductivity as found in the heavy-fermions, high-transition-temperature (high-Tc) cuprates, and iron pnictides superconductors is that the superconductivity emerges in the vicinity of long-range antiferromagnetically ordered state.[1] In addition to doping charge carriers, the application of external physical pressure has been taken as an effective and clean approach to induce the unconventional superconductivity near a magnetic quantum critical point (QCP).[2,3] Superconductivity has been observed in a majority of 3d transition-metal compounds,[4-9] except for the Cr- and Mn-based compounds in the sense that the low-lying states near Fermi level are dominated by their 3d electrons. Herein, we report on the discovery of superconductivity on the verge of antiferromagnetic order in CrAs via the application of external high pressure. Bulk superconductivity with Tc ~ 2 K emerges at the critical pressure Pc ~ 8 kbar, where the first-order antiferromagnetic transition at TN = 265 K under ambient pressure is completely suppressed. Abnormal normal-state properties associated with a magnetic QCP have been observed nearby Pc. The close proximity of superconductivity to an antiferromagnetic order suggests an unconventional pairing mechanism for the superconducting state of CrAs. The present finding opens a new avenue for searching novel superconductors in the Cr and other transitional-metal based systems.