Asia Pacific Physics Week 2023 (APPW2023)

Tuesday, Nov. 7, 2023 

3:30 PM - 4:10 PM  Plenary Talk  Xiangang Wan (Nanjing University) 

Possible structural distortion from symmetry analysis and electron-correlation-induced charge density wave in FeGe

Xiangang Wan

Department of Physics, Nanjing University, Nanjing 210093, China

As the first magnetic kagome material to exhibit the charge density wave (CDW) order, FeGe has attracted much attention in recent studies. The theoretically calculated phonon frequencies in FeGe remain positive. We perform a comprehensive study through first-principles calculations and symmetry analysis. We find that reasonable Heisenberg interactions and magnetic anisotropy cannot explain the double cone magnetic transition, and the net DM interactions, which cannot exist in the structure with mirror symmetry or inversion symmetry, is need for this small magnetic cone angle. Based on the experimental 2X2X2 supercell, we thus explore the subgroups of the parent phase. Group theoretical analysis reveals that there are 68 different distortions, and only four of them without inversion and mirror symmetry thus can explain the low temperature magnetic structure. We also find that the maximum of nesting function is at K point instead of M point. Considering the effect of local Coulomb interaction, we reveal that the Fermi level eigenstates nested by vector K are mainly distributed from unequal sublattice occupancy, thus the instability at K point is significantly suppressed. Meanwhile, the wave functions nested by vector M have many ingredients located at the same Fe site, thus the instability at M point is enhanced. This indicates that the electron correlation, rather than electron-phonon interaction, plays a key role in the CDW transition at M point.