Microscopic origin of period-four stripe charge density wave in the kagome metal CsV 3 Sb 5

The interplay between unconventional density waves and exotic superconductivity has attracted growing interest. Kagome superconductors AV₃Sb₅ (A = K, Rb, Cs) offer a platform for studying quantum phase transitions and the resulting symmetry breaking. Among these quantum phases, the 4a₀ stripe charge-density-wave (CDW) has been widely observed for A=Rb and Cs by scanning tunneling microscopy (STM) and nuclear magnetic resonance (NMR) measurements. However, the microscopic origin of the 4a₀ stripe CDW remains elusive, and no theoretical studies addressing this phenomenon have been reported so far. In this paper, we propose a microscopic mechanism for the emergence of the 4a₀ stripe CDW. We analyze the CDW instability in the 12-site kagome lattice Hubbard model with the 22 bond order driven by the paramagnon-interference mechanism by focusing on the short-range magnetic fluctuations due to the geometrical frustration of kagome lattice. We reveal that the nesting vector of the reconstructed Fermi surface, formed by the 2 2 bond order, gives rise to a 4a₀-period CDW. Remarkably, the obtained stripe CDW is composed of both the off-site hopping integral modulations and on-site potentials. The real-space structure of the stripe CDW obtained here is in good qualitative agreement with the experimentally observed stripe pattern.