The origin of diverse nematicity and their order parameters in Fe-based superconductors have been attracting increasing attention. Recently, a new type of nematic order has been discovered in heavily hole-doped (n_d=5.5) compound AFe₂As₂(A=Cs,Rb). The discovered nematicity has B₂g(=d_xy) symmetry, rotated by 45∘ from the B_1g(=d_x2−y2) nematicity in usual compounds with n_d≈6. We predict that the “nematic bond order,” which is the symmetry breaking of the correlated hopping, is responsible for the B_2g nematic order in AFe₂As₂. The Dirac pockets in AFe₂As₂ is essential to stabilize the B_2g bond order. Both B_1g and B_2g nematicity in A_1−xBa_xFe₂As₂ are naturally induced by the Aslamazov-Larkin many-body process, which describes the spin-fluctuation-driven charge instability. The present study gives a great hint to control the nature of charge nematicity by modifying the orbital character and the topology of the Fermi surface.

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