Physical properties and electronic structure of single-crystal KCo$_2$As$_2$

TL;DR

This study reports high-quality single crystals of KCo2As2, analyzing its structure, electronic properties, and unusual magnetoresistance, revealing weaker electron correlations and a simple Fermi surface compared to similar compounds.

Contribution

It introduces a reliable method for producing high-quality KCo2As2 crystals and provides comprehensive experimental insights into its electronic structure and magnetic properties.

Findings

High-quality, air-stable KCo2As2 crystals synthesized.

Absence of magnetic order down to 2 K.

Large linear magnetoresistance of 200% at 14 T.

Abstract

We present a method for producing high quality KCo2As2 crystals, stable in air and suitable for a variety of measurements. X-ray diffraction, magnetic susceptibility, electrical transport and heat capacity measurements confirm the high quality and an absence of long range magnetic order down to at least 2 K. Residual resistivity values approaching 0.25 $\mu\Omega$~cm are representative of the high quality and low impurity content, and a Sommerfeld coefficient $\gamma$ = 7.3 mJ/mol K$^2$ signifies weaker correlations than the Fe-based counterparts. Together with Hall effect measurements, angle-resolved photoemission experiments reveal a Fermi surface consisting of electron pockets at the center and corner of the Brillouin zone, in line with theoretical predictions and in contrast to the mixed carrier types of other pnictides with the ThCr2Si2 structure. A large, linear magnetoresistance of 200\% at 14~T, together with an observed linear and hyperbolic, rather than parabolic, band dispersions are unusual characteristics of this metallic compound and may indicate more complex underlying behavior.