Effect of on-site Coulomb repulsion on ferromagnetic fluctuations in heavily over-doped cuprates

Abstract

We theoretically study ferromagnetic (FM) fluctuations that are experimentally observed in the heavily overdoped region of cuprate superconductors. To explore the origin of FM fluctuations, we evaluate the spin susceptibilities of a single-band Hubbard model within the fluctuation exchange approximation. Model parameters are derived using the Wannierization technique and the constrained random phase approximation method based on the maximally localized Wannier functions. The constrained random phase approximation calculations reveal that the on-site Coulomb interaction decreases with an increase in hole doping. By taking this reduction of the on-site Coulomb interaction into account, the emergence of FM fluctuations in heavily overdoped cuprates can be explained.

Magnetic Impurity Effects on Ferromagnetic Fluctuations in Heavily Overdoped (Bi,Pb)$_2$Sr$_2$Cu$_{1-y}$Fe$_y$O$_{6+δ}$ Cuprates

“…The quantum critical scaling theory in HOD Tl 2 Ba 2 CuO 6+δ suggested that the enhancement of the magnetic susceptibility χ at low temperatures is caused by ferromagnetic fluctuations due to itinerant electrons. 11) The development of the ferromagnetic fluctuations in the HOD cuprates was also suggested from the theoretical calculations in which the spectral * E-mail: t-adachi@sophia.ac.jp weight of the spin dynamical structure factor 12) and the spin susceptibility 13,14) were enhanced around Q = (0, 0). Experimentally, a three-dimensional (3D) ferromagnetic order due to itinerant electrons was suggested in HOD La 2−x Sr x CuO 4 from µSR and transport measurements.…”