Competing charge density wave and antiferromagnetism of metallic atom wires in GaN(10${\overline{1}}$0) and ZnO(10${\overline{1}}$0)

TL;DR

This study uses advanced DFT calculations to explore the competing charge density wave and antiferromagnetic phases in metallic atom wires on GaN and ZnO surfaces, revealing how electron localization influences the ground state.

Contribution

It provides a systematic comparison of the ground states of DB wires on GaN and ZnO surfaces using multiple DFT methods, highlighting the role of electron localization in phase stability.

Findings

GaN DB wires favor AFM order due to localized electrons.

ZnO DB wires favor CDW formation with less localized electrons.

Different computational methods predict different ground states for the same systems.

Abstract

Low-dimensional electron systems often show a delicate interplay between electron-phonon and electron-electron interactions, giving rise to interesting quantum phases such as the charge density wave (CDW) and magnetism. Using the density-functional theory (DFT) calculations with the semilocal and hybrid exchange-correlation functionals as well as the exact-exchange plus correlation in the random-phase approximation (EX + cRPA), we systematically investigate the ground state of the metallic atom wires containing dangling-bond (DB) electrons, fabricated by partially hydrogenating the GaN(10${\overline{1}}$0) and ZnO(10${\overline{1}}$0) surfaces. We find that the CDW or antiferromagnetic (AFM) order has an electronic energy gain due to a band-gap opening, thereby being more stabilized compared to the metallic state. Our semilocal DFT calculation predicts that both DB wires in GaN(10${\overline{1}}$0) and ZnO(10${\overline{1}}$0) have the same CDW ground state, whereas the hybrid DFT and EX+cRPA calculations predict the AFM ground state for the former DB wire and the CDW ground state for the latter one. It is revealed that more localized Ga DB electrons in GaN(10${\overline{1}}$0) prefer the AFM order, while less localized Zn DB electrons in ZnO(10${\overline{1}}$0) the CDW formation. Our findings demonstrate that the drastically different ground states are competing in the DB wires created on the two representative compound semiconductor surfaces.