Ubiquitous van der Waals altermagnetism with sliding/moire ferroelectricity

TL;DR

This paper demonstrates that stacking and twisting 2D van der Waals layers can induce altermagnetism and ferroelectricity, revealing new physics and potential applications in spintronics.

Contribution

It introduces a novel strategy to induce altermagnetism in 2D materials using multilayer stacking and moire engineering, expanding the scope of altermagnetic phenomena.

Findings

Co-existence of sliding ferroelectricity and altermagnetism in multilayers.

Moire ferroelectricity combined with altermagnetism upon twisting.

Pseudo-altermagnetism with zero net magnetization in untwisted bilayers.

Abstract

According to the recent studies on sliding/moire ferroelectricity, most 2D van der Waals nonferroelectric monolayers can become ferroelectric via multilayer stacking. In this paper we propose that similar strategy can be used to induce desirable van der Waals altermagnetism with symmetry-compensated collinear magnetic orders and non-relativistic spin splitting. Our first-principles calculations show the pervasive co-existence of sliding ferroelectricity and altermagnetism in a series of magnetic multilayers with anti-parallel stacking configurations. Upon a twist angle in bilayers, moire ferroelectricity can be combined with altermagnetism, while some untwisted bilayers exhibit pseudo-altermagnetism with zero net magnetizations and non-relativistic spin splittings coupled with sliding ferroelectricity. Our study significantly expands the scope of altermagnetism, and its combination with sliding/moire ferroelectricity brings in new physics as well as promising applications, which should stimulate further experimental efforts.