Probing Altermagnetic Band Splitting and Fermi Surface Reconstruction in the Distorted Kagome Metal CsCr3Sb5

We propose to perform high-resolution angle-resolved photoemission spectroscopy (ARPES) and spin-resolved ARPES to investigate the predicted altermagnetic ground state in the Cr-based kagome metal CsCr₃Sb₅ - a correlated system that hosts a rich interplay of magnetism, charge order, electron correlations, and superconductivity [1-7]. Altermagnetism has recently been recognized as a unique magnetic phase that is different from traditional magnetism and is defined by collinear spin alignment, which disrupts time-reversal and rotational symmetries while preserving zero net magnetization [8,9]. This symmetry breaking leads to momentum-dependent spin splitting of electronic bands without the need for spin-orbit coupling, instead driven by complex crystallographic symmetries like glide mirrors. First-principles calculations predict that CsCr₃Sb₅ stabilizes a complex 4x2 spin-density-wave (SDW) state, accompanied by a lattice distortion and the emergence of a spin-polarized Fermi surface, all in the absence of spin-orbit interaction. This type of symmetry-protected spin splitting cannot be observed through traditional methods like magnetometry or transport, but can be effectively accessed through momentum-resolved spectroscopies like ARPES. The primary objective of this experiment is to identify and analyze the spin-split bands and Fermi surface reconstructions, which can provide direct experimental evidence of alternamagnetism in a metallic Kagome structure. Experimental success will not only validate the theoretical predictions but also open up new frontiers in the study of non-relativistic spin-polarized states with broad implications in the field of topological spintronics.