Magnetic correlations in the pressure-induced superconductor CrAs investigated by $^{75}$As nuclear magnetic resonance

TL;DR

This study uses $^{75}$As-NMR to explore how pressure induces superconductivity in CrAs, revealing unusual magnetic correlations linked to its crystal structure that differ from typical antiferromagnetic materials.

Contribution

It provides the first detailed NMR analysis of pressure-induced superconductivity in CrAs, highlighting its unique magnetic properties and their relation to the crystal symmetry.

Findings

Knight shift indicates increasing spin susceptibility at low temperatures.

Superconductivity appears alongside unusual magnetic correlations.

Magnetic behavior is influenced by the three-dimensional zigzag structure.

Abstract

We report $^{75}$As-NMR results for CrAs under pressure, which shows superconductivity adjoining a helimagnetically ordered state. We successfully evaluated the Knight shift from the spectrum, which is strongly affected by the quadrupole interaction. The Knight shift shows the remarkable feature that the uniform spin susceptibility increases toward low temperatures in the paramagnetic state. This is in sharp contrast to CrAs at ambient pressure, and also to cuprates and Fe pnictides, where antiferromagnetic correlations are dominant. Superconductivity emerges in CrAs under unique magnetic correlations, which probably originate in the three-dimensional zigzag structure of its nonsymmorphic symmetry.