Pushing an Altermagnet to the Ultimate 2D Limit: Evidence of Symmetry Breaking in Monolayers of GdAlSi

Abstract

Altermagnets have emerged as a class of materials combining certain ferromagnetic properties with zero net magnetization. This combination is highly promising for spintronics, especially if a material can be brought to a nanoscale size. However, experimental studies of the 2D limit of altermagnets and evolution of their properties with thickness are lacking. Here, we study epitaxial films on silicon of the Weyl altermagnet GdAlSi ranging from more than a hundred unit cells to a single unit cell. The films are synthesized by molecular beam epitaxy and, expectedly, do not show any discernible net magnetic moments. Electron transport studies reveal a remarkable transformation of the electron state with the film thickness. Thick films exhibit negative longitudinal magnetoresistance associated with the chiral anomaly but do not demonstrate altermagnetic properties in electron transport due to symmetry restrictions. In ultrathin films, a spontaneous anomalous Hall effect manifests itself, indicating a non-relativistic spin splitting in the electronic structure. The transformation is associated with crystal symmetry breaking accompanying the 3D-to-2D crossover. The work highlights the role of dimensionality in altermagnetism and provides a platform for studies of altermagnets aiming at ultra-compact spintronics.

References in corpus (28)

• Multifunctional Antiferromagnetic Materials with Giant Piezomagnetism and Noncollinear Spin Current
• Broken Kramers' degeneracy in altermagnetic MnTe
• Tilted spin current generated by the collinear antiferromagnet RuO2
• Altermagnetism: Exploring New Frontiers in Magnetism and Spintronics
• Direct observation of altermagnetic band splitting in CrSb thin films
• Spontaneous anomalous Hall effect arising from an unconventional compensated magnetic phase in a semiconductor
• Altermagnetic Routes to Majorana Modes in Zero Net Magnetization
• Review of experiments on the chiral anomaly in Dirac-Weyl semimetals
• Two-dimensional altermagnets: Superconductivity in a minimal microscopic model
• Saturation of the anomalous Hall effect at high magnetic fields in altermagnetic RuO2
• Anisotropy of the anomalous Hall effect in the altermagnet candidate Mn${}_5$Si${}_3$ films
• Observation of Weyl fermions in a magnetic non-centrosymmetric crystal
• Room temperature two-dimensional antiferromagnetic Weyl semimetal CrO with giant spin-splitting and spin-momentum locked transport
• Essential role of anisotropic magnetic dipole in anomalous Hall effect
• Interplay of altermagnetism and weak ferromagnetism in two-dimensional RuF${}_4$
• Towards Weyltronics: Realization of epitaxial NbP and TaP Weyl Semimetal thin films
• Altermagnetic surface states: towards the observation and utilization of altermagnetism in thin films, interfaces and topological materials
• Observation of Fermi arcs and Weyl nodes in a non-centrosymmetric magnetic Weyl semimetal
• Wurtzite vs rock-salt MnSe epitaxy: electronic and altermagnetic properties
• High mobility charge transport in a multicarrier altermagnet CrSb
• GdAlSi: An antiferromagnetic topological Weyl semimetal with non-relativistic spin splitting
• Induced Monolayer Altermagnetism in MnP(S,Se)${}_3$ and FeSe
• Monolayer Magnetic Metal with Scalable Conductivity
• Observation of Giant Spin Splitting and d-wave Spin Texture in Room Temperature Altermagnet RuO2
• Altermagnetic Polar Metallic phase in Ultra-Thin Epitaxially-Strained RuO2 Films
• Engineering of a Layered Ferromagnet via Graphitization: An Overlooked Polymorph of GdAlSi
• Observation of non-volatile anomalous Nernst effect in altermagnet with collinear Néel vector
• Crystal design of altermagnetism

Cited by in corpus (5)

• Spin-Polarized Antiferromagnetic Spintronics
• Electric-Field-Controlled Altermagnetic Transition for Neuromorphic Computing
• Dirac edge states as signature of two-dimensional altermagnetic topological crystalline phase
• Emergent Magnetic Structures at the 2D Limit of the Altermagnet MnTe
• Spontaneous emergence of altermagnetism in the single-orbital extended Hubbard model