Density waves in low-pressure bilayer nickelates

The low-pressure phase diagram of La 3 Ni 2 O 7 provides an important reference for understanding its pressure-induced high-temperature superconductivity. While the spin-density-wave transition at T SDW about150 K is increasingly well established, the origin of the second density-wave transition at T DW about130 K has remained unresolved. Here, we perform unrestricted Hartree-Fock calculations to investigate the potential origin of the second transition. Within the orthorhombic phase, the degeneracy between possible ordering wavevectors at Y=(0,π) and at X=(π,0) is lifted and the electronic system develops a double-stripe spin-density wave with ordering vector Y=(0,π). We identify that the pure double stripe spin state is unstable in La 3 Ni 2 O 7 towards a commensurate charge-density wave instability, which favors a spin-modulated double stripe order with intertwined charge and spin instabilities and establish the hierarchy of ordered states in La 3 Ni 2 O 7. We further discuss our results in the context of available experimental literature and propose further experimental tests to elucidate the origin of the SDW/DW states in this system.