Optical Controllable Spin-Polarization in Two Dimensional Altermagnets via Robust Spin-Momentum Locking Excitons

TL;DR

This paper predicts the existence of intrinsically spin-momentum locked excitons in two-dimensional altermagnetic materials, which are stable at room temperature and can be optically controlled for ultrafast spintronics applications.

Contribution

It introduces a new class of SML excitons in altermagnetic V$_2 X_2$O monolayers with high binding energies and long lifetimes, driven by giant non-relativistic spin-splittings.

Findings

SML excitons with binding energies >1400 meV in monolayers.

Stacking-dependent optical selection rules enable tunable interlayer excitons.

Long radiative lifetimes suggest room-temperature spin-polarization stability.

Abstract

Spin-momentum locking (SML) excitons in two-dimensional semiconductors are appealing to programmable optical control of spin-polarized carriers in ultrafast spintronics. To address the current thirsty for long-lived excitons with zero-external-field stability and room-temperature spin-polarization, we hereby predict the existence of intrinsically SML excitons in altermagnetic V$_2 X_2$O ($X=$ S, Se) driven by giant non-relativistic spin-splittings ($>$ 1.2 eV). First-principles calculations reveal SML excitons with binding energies exceeding 1400 meV in monolayers and 430 meV in their van der Waals heterobilayers, along with stacking-dependent optical selection rules for tunable interlayer excitons. These remarkable physical properties, combined with their long radiative lifetimes, strongly suggest the feasibility of SML excitons with robust spin-polarization at room temperature. Our work provides a new paradigm for SML exciton physics via the novel altermagnetism, opening up new possibilities for all-optical manipulation in advanced opto-spintronics.