Sliding Engineering Spin-Valley-Layer Coupling and Altermagnetism in Bilayer Antiferromagnetic Honeycomb Lattices

TL;DR

This paper proposes a method to achieve ferroelectric-valley and ferroelectric-altermagnetic coupling in bilayer antiferromagnetic honeycomb lattices, validated by first-principles calculations on MnPTe3, enabling electric control of valley and spin properties for advanced 2D spintronic devices.

Contribution

It introduces a novel approach to electrically control valley and spin degrees of freedom in 2D antiferromagnets through stacking and polarization switching, demonstrating dual control of valley polarization and spin splitting.

Findings

Reversible polarization switching via interlayer sliding.

Polarization reversal inverts valley polarization and spin splitting.

Enables tunable valley Hall effects and magnetoelectric responses.

Abstract

Valley polarization and altermagnetism are two emerging fundamental phenomena in condensed matter physics, offering unprecedented opportunites for information encoding and processing in novel energy-efficient devices. By coupling valley and spin degrees of freedom with ferroic orders such as ferroelectricity, nonvolatile memory functionalities can be achieved. Here, we propose a way to realize ferroelectric-valley (FE-valley) and FE-altermagnetic coupling in a bilayer antiferromagnetic (AFM) honeycomb lattices based on an effective four-band spin-full $k\cdot p$ model. Our proposal is validated in bilayer MnPTe$_3$ through first-principles calculations. A spontaneous out-of-plane electric polarization occurs in AB- (BA-) stacking configuration, which is reversibly switchable via interlayer sliding. Remarkably, polarization reversal simultaneously inverts both layer-resolved valley polarization and altermagnetic spin splitting. This dual control enables tunable layer-spin-locked anomalous valley Hall effects and an unprecedented magnetoelectric response in 2D antiferromagnets. Our work establishes a general paradigm for electrically programmable valleytronic and spintronic functionalities of 2D AFM materials.