Magnetic surface on nonmagnetic bulk of electride Hf2S

TL;DR

This study reveals that multilayer Hf2S electride exhibits magnetic surface states with unique transport phenomena, combining first-principles calculations to predict novel magnetic and electronic properties in a recently synthesized electride material.

Contribution

It is the first theoretical investigation showing magnetic surface states and unusual transport effects in Hf2S electride, expanding understanding of 2D electrides.

Findings

Surface Hf atoms and electron gas are spin polarized.

Multilayer Hf2S shows surface anomalous Hall effect.

Predicted electric-field-induced layer Hall effect.

Abstract

Recent experiment reported the self-passivated electride Hf2S with excellent stability and continuous electrocatalytic ability [S. H. Kang et al., Sci. Adv. 6, eaba7416 (2020)]. Starting from its 2H-type layered structure, we have studied the electronic, magnetic, and transport properties of the electride Hf2S in the monolayer and multilayer forms by combining first-principles electronic structure calculations and Kubo formula approach. Our calculations indicate that these thin films of Hf2S electride are both dynamically and thermodynamically stable. Astonishingly, the calculations further show that the outmost Hf atoms and the surface electron gas of the Hf2S multilayers are spin polarized, while the inner Hf atoms and the electron gas in the interlayer regions remain nonmagnetic. Due to the magnetic surface, the multilayer Hf2S exhibits many unusual transport properties such as the surface anomalous Hall effect and the electric-field-induced layer Hall effect. Our theoretical predictions on Hf2S call for future experimental verification.