Fractional Corner Charge of Sodium Chloride

Recent developments in higher-order topological phases have elucidated on the relationship between nontrivial multipole moments in the bulk and the emergence of fractionally quantized charges at the boundary. Here, we put on the table a proposal of the three-dimensional octupole insulator with fractionally quantized corner charges ±e/8: sodium chloride, commonly known as table salt. We further show that the electrostatic signature of the fractional charge is well-preserved even when the ideal crystal is sprinkled with defects. Our results suggest that the observation of corner charges from quantized multipole moments in solids might be around the corner.