A route to fully-compensated ferrimagnetic metal: electric-field annihilation of the bilayer bandgap

TL;DR

This paper proposes a method to create fully-compensated ferrimagnetic metals by electrically closing the bilayer gap in 2D materials, validated through first-principles calculations on specific examples.

Contribution

It introduces a novel approach to realize FC-FIM metals via electric-field control in 2D systems, expanding the possibilities beyond traditional gapped states.

Findings

Electric field can annihilate the bilayer gap in specific 2D systems.

FC-FIM metal achieved only with AFM interlayer coupling and UMS building blocks.

Validated approach using first-principles calculations on bilayer MnOF, bilayer ScI2, and monolayer Hf2S.

Abstract

Fully-compensated ferrimagnet has garnered widespread attention due to its zero-net total magnetic moment and non-relativistic global spin splitting. In general, for a fully-compensated ferrimagnet, at least one spin channel should be gapped to ensure a zero-net total magnetic moment, which would lead to a fully-compensated ferrimagnetic (FC-FIM) semiconductor or half-metal, and appears to limit the existence of an FC-FIM metal. Here we propose that an FC-FIM metal can be achieved by electrically closing the gap of a bilayer system. Using two-dimensional (2D) ferromagnetic (FM) semiconductor as building block, we examine both FM and antiferromagnetic (AFM) interlayer couplings and distinguish unipolar magnetic semiconductor (UMS) and bipolar magnetic semiconductor (BMS) monolayers. It is concluded that an electric field can annihilate the bilayer gap and realize the FC-FIM metal only when the interlayer coupling is AFM and the building block is a UMS. Our scheme for realizing an FC-FIM metal can be generalized to electrically tuned 2D spin-degenerate metal with spin-layer locking. Using first-principles calculations, we have validated our proposal by taking bilayer MnOF, bilayer $\mathrm{ScI_2}$ and monolayer $\mathrm{Hf_2S}$ as examples. Our work offers an alternative route to realize the originally forbidden FC-FIM metal, paving the way for further exploration of FC-FIM metal.