Switchable Giant Spin Injection Current in Janus Altermagnet Fe$_2$SSeO

TL;DR

This paper demonstrates a novel spin photovoltaic effect in 2D Janus altermagnetic Fe$_2$SSeO, enabling controllable giant spin injection currents for advanced spintronic applications.

Contribution

It introduces a symmetry-allowed spin photovoltaic effect in 2D altermagnets, specifically identifying Janus Fe$_2$SSeO as a candidate for controllable spin injection.

Findings

Janus Fe$_2$SSeO exhibits polarization-dependent injection conductivity of ~1200 μA/V².

Giant spin injection current can be switched by rotating magnetization and applying strain.

The mechanism is distinct from $ ext{PT}$-antiferromagnets, involving spin-momentum locking under linearly polarized light.

Abstract

Generating and controlling spin current in miniaturized magnetic quantum devices remains a central objective of spintronics, due to its potential to enable future energy-efficient information technologies. Among the existing magnetic phases, altermagnetism have recently emerged as a highly promising platform for spin current generation and control, going beyond ferromagnetism and antiferromagnetism. Here, we propose a symmetry-allowed spin photovoltaic effect in two-dimensional (2D) altermagnetic semiconductors that enables predictable control of giant spin injection currents. Distinct from parity-time ($\mathcal{PT}$)-antiferromagnets, Janus altermagnetic semiconductors generate not only shift current but also a unique injection current with spin momentum locked in a specific direction under linearly polarized light -- a mechanism absent in $\mathcal{PT}$-antiferromagnets. Through symmetry analysis and first-principles calculations, we identify Janus Fe$_2$SSeO as a promising candidate. Specifically, the monolayer Fe$_2$SSeO exhibits a polarization-dependent injection conductivity reaching $\sim$1,200~$\mu$A/V$^{2}\!\cdot\!\hbar/2e$, and the giant spin injection current can be effectively switched by rotating the magnetization direction and engineering strains. These findings underscore the potential of 2D altermagnets in spin photovoltaics and open avenues for innovative quantum devices.