Complex structure due to As bonding and interplay with electronic structure in superconducting BaNi2As2

TL;DR

This study reveals two competing structural phases in BaNi2As2 driven by arsenic bonding, influencing its electronic properties and phase behavior, supported by first-principles calculations and photoemission experiments.

Contribution

It uncovers the existence of two distinct structural phases in BaNi2As2 and explains their electronic and bonding differences through first-principles calculations and experimental validation.

Findings

Two competing structures close in energy.

Complex As bonding patterns drive Ni layer distortions.

Electronic transport becomes anisotropic due to structural interplay.

Abstract

BaNi2As2 is a superconductor chemically related to the Fe-based superconductors, with a complex and poorly understood structural phase transition. We show based on first principles calculations that in fact there are two distinct competing structures. These structures are very different from electronic, transport and bonding points of view but are close in energy. These arise due to complex As bonding patterns and drive distortions of the Ni layers. This is supported by photoemission experiments. This leads to an interplay of electronic and structural behavior including induced anisotropic of the electronic transport. The competition between these distortions is associated with the complex behavior observed in BaNi2As2 samples.