η-pairing in photodoped mix-D Hubbard Model*

Strong excitations of correlated quantum materials give rise to various non-thermal phases which are not present in their equilibrium counterpart. Recently, it was shown that the one-dimensional Fermi Hubbard Model features charge density wave and η - pairing phases upon photo-doping.

We will present a study of such non-thermal phases in the mix-D Fermi Hubbard model. Using the Schrieffer-Wolff transformation, we map the mix-D Fermi Hubbard model to a t-J-like model, which gives a simplified and effective equilibrium description of the photo-doped states. An applied electric field allows us to tune the asymmetry in between the intra-chain J, and inter-chain exchange energy J₁. Our main finding is that the binding energy of photo-doped charge carriers changes compared to a chemically doped one due to the η-pairing in such a system. We characterize the ground state of this system using appropriate correlators at both the isotropic ( J = J₁) and strong anisotropic coupling ( J >> J₁) limits. At strong anisotropy, the ground state includes a strongly bound doublon-hole pair along the rung, and inter-chain singlets. We can analytically show the influence of η-pairing fluctuations on binding energy and the dynamics of the bound pair. Finally, to ensure that our results are robust in the thermodynamic limit, we use tensor network algorithms to go to higher system sizes.