Observation of Berry curvature and chirality in Mn3Ge Weyl semimetal using polarized SANS

Antiferromagnetic (AFM) Weyl semimetals, such as Mn3Ge, are topological materials exhibiting anomalous transport properties, including the anomalous Hall effect (AHE), anomalous magneto-optic Kerr effect (MOKE), and anomalous Nernst effect, all driven by nonvanishing Berry curvature. Mn3Ge stands out for its noncollinear AFM structure in the a-b plane, which breaks time-reversal symmetry, resulting in a large Berry curvature. This Berry curvature, arising from broken time-reversal symmetry, acts like an intrinsic magnetic field, leading to real-space effects similar to ferromagnetic (FM) materials. Since neutrons also sense the Berry phase, we propose that small-angle neutron scattering (SANS) of AFM Weyl semimetals, such as Mn3Ge, will show field-dependent patterns akin to those observed in FM systems. This experiment could provide new insights into the interaction between neutrons and Berry phase. Moreover, when a small magnetic field (at least 20 mT) is applied in the x-y crystallographic plane, an imbalance of magnetic domains with specific (net) chirality is created, leading to nonzero Berry curvature and observable effects like AHE and MOKE. We anticipate that the net chirality of magnetic domains can be detected using polarized SANS (SANSPOL), revealing asymmetry in the SANS cross-section when the magnetic field is applied within the x-y plane. This experiment will enhance the understanding of Berry curvature and chiral magnetism in AFM systems.