New Era of Magnetization: Research sheds light on future applications of spitronics and valetronics

ALTERTERGINESTS, which exhibits momentum-dependent spin splitting without spin-orbit coupling (SOC) or net magnetization, has recently attracted a great deal of international attention.

A team led by Professor Liu Junwei of the Department of Physics at Hong Kong University of Science and Technology (HKUST) has published the latest research findings in natural physics, along with experimental collaborators.

Implementation and control of spin-polarized electronic states in solids is important for spintronics for encoding and processing. Spin-polarized light is usually produced by combining electron spins with other degrees of freedom, such as orbitals and magnetic moments.

This involves SOCs, which generates momentum-dependent spin splitting or ferromagnetic time-inverting symmetry of non-inverting symmetric crystals (Rashba – Dresselhaus effect), resulting in momentum-independent Zeeman-type spin splitting.

In their study, Professor Li and others proposed a new mechanism of spin splitting in anti-ferromagnets that allows sublatics connected by crystal symmetry to generate exchange couplings and important spin splitting in a unique C-pair spin valley lock.

This effect combines the stability of antiferromagnetic devices with long spin-life stability and is independent of SOC or net magnetization. These unconventional anti-ferromagnets are called “ALTERTERGENETS” and their discoveries were recognized as one of the top 10 breakthroughs of science in 2024.

Despite extensive theoretical and experimental efforts to explore unconventional antiferromagnets based on emerging materials such as α-MNTE, CRSB, MNTE2, and RUO2, none meets the spin current symmetry and conductivity requirements associated with inphasic spins by ALETERAGNETIST. The magnetic sublattices of α-MNTE and CRSB have C₃symmetry, leading to isotropic conductance and non-polar currents.

In MNTE2, spins are not preserved due to non-coplanar magnetic structures, and a low critical temperature (87 K) limits practical applications. In the case of RUO2, despite evidence of anomalous Hall effects and spin splitting, whether its ground state is antiferromagnetic or nonmagnetic is debated. Furthermore, these materials are not layered and limit the possibility of peeling and integration with other materials in order to control their properties at the microscope level.

This limitation hinders investigation of the effects of 2D materials such as superconducting proximity effects, tunable electronic properties via gating, and topological superconductors via moire’s ultra-lattice.

Therefore, it is essential to explore layered materials with ALTERTERGINESTS to develop high density, high speed, and low energy consumption spintronic devices. Professor Li’s observation of a two-dimensional layered room temperature pleural magnet shines new light on this area.

Based on theoretical predictions by Professor Liu’s team of V2TE2O and V2SE2O in 2021, this work illustrates the realization of C-pair spin valley lock (SVL) in layered room temperature anti-strong magnet (AFM) compounds RB1-ΔV2TE2O using layered compound RB1-ΔV2TE2O using spin and angle photoelectroscopy. Microscopy/spectroscopy (STM/STS), and first-principles calculations.

Important findings include direct observation of C-paired SVLs by spin arc measurements. This reveals opposite spin polarization signs between adjacent X and Y valleys connected by crystal symmetric C.

Temperature-dependent ARPES measurements show SVL stability to room temperature, consistent with the AFM phase transition temperature. Furthermore, ARPES measurements confirm strong two-dimensional properties with negligible dispersion in the KZ direction, whereas quasiparticle interference patterns from the STM map reveal suppressed valley-to-valley scattering due to spin selection rules.

Professor Liu’s work shows the first layered room temperature AFM metal with magnetic subimages and a new type of spin-splitting effect, providing an ideal platform for further research and applications of spitronics and valetronics.

Importantly, all experimental results fit well with first-principles calculations, strengthening confidence in theoretical research, suggesting potential access to spin-conserved currents and unconventional piezotumors.

A similar spin volleylock has also been observed in the K insertion V2SE2O, further examining Professor Li’s theoretical predictions for 2021.