Spiral electronic structure of chiral crystal NbSi₂

Recently, so-called chirality induced spin selectivity effect has been observed in the chiral crystal NbSi₂ through electrical conductivity measurement [1,2]. To investigate the electronic structure of NbSi₂, we performed synchrotron-radiation angle resolved photoemission spectroscopy for both right-(P6₂22) and left-handed (P6₄22) samples. Since the NbSi₂ crystal is difficult to cleave, the clean surface was obtained by mechanical polishing, Ar ion sputtering and annealing. We found not only the clear energy bands, but also spiral-shaped constant energy contours at specific binding energies. The fact that the helicity of this pattern is reversed in the crystal having opposite chirality indicates that the observed intriguing pattern has its origin in the structural chirality. This result demonstrates that a photoemission experiment can be a new way to distinguish the chirality of crystals. Furthermore, in the presentation we will also discuss the possible origin of the spiral pattern based on the results of DFT calculations.