Spin-layer coupling in altermagnets multilayer: a design principle for spintronics

TL;DR

This paper investigates spin-layer coupling in altermagnet multilayers, revealing how symmetry and external fields can control spin splitting, with implications for designing energy-efficient spintronic devices.

Contribution

It introduces a general design principle for spin-layer coupling in altermagnet multilayers based on symmetry analysis and explores how magnetic order and external fields modulate spin splitting.

Findings

Spin splitting can be modulated by symmetry, magnetic order, and external fields.

Odd-layer Cr2S2 exhibits coexistence of spin splitting and degeneracy.

Spin-layer coupling shows strong odd/even-layer dependence.

Abstract

The discovery of collinear symmetric-compensated altermagnets (AM) with intrinsic spin splitting provides a route towards energy-efficient and ultrafast device applications. Here, using first-principles calculations and symmetry analysis, we propose a series of AM Cr2SX (X=O, S, Se) monolayer and explore the spin splitting in Cr2SX multilayer. A general design principle for realizing the spin-layer coupling in odd/even-layer is mapped out based on the comprehensive analysis of spin group symmetry. The spin splitting behavior related with the MzUt, Mz and ML symmetries in AM multilayer can be significantly modulated by magnetic orders, crystal symmetry and external perpendicular gate field (Ez). Due to the spin-compensated bands of sublayers linked by overall Mz and interlayers ML symmetries, the Cr2S2 odd-layer exhibits the unique coexistence of spin splitting and spin degeneracy at high symmetric paths and X/Y valley, respectively. Furthermore, owing to the higher priority of overall ML symmetry compared to interlayers ML symmetry in AM even-layer, the spin-layer coupling of AM multilayer shows strong odd/even-layer dependence. Our work not only offer a new direction for manipulating spin splitting, but also greatly enrich the research on AM monolayer and multilayer.