Theory of electron-hole asymmetry in dopedCuO2planes

The magnetic phase diagrams, and other physical characteristics, of the hole-doped ${\mathrm{La}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Sr}}_{\mathit{x}}$ ${\mathrm{CuO}}_4$ and electron-doped ${\mathrm{Nd}}_{2\mathrm{-}\mathit{x}}$ ${\mathrm{Ce}}_{\mathit{x}}$ ${\mathrm{CuO}}_4$ high-temperature superconductors are profoundly different. Given that it is envisaged that the simplest Hamiltonians describing these systems are the same, viz., the t-t’-J model, this is surprising. Here we relate these physical differences to their ground states’ single-hole quasiparticles, the spin distortions they produce, and the spatial distribution of carriers for the multiply doped systems. As is well known, the low doping limit of the hole-doped material corresponds to k=(π/2,π/2) quasiparticles, states that generate so-called Shraiman-Siggia long-ranged dipolar spin distortions via backflow. These quasiparticles have been proposed to lead to an incommensurate spiral phase, an unusual scaling of the magnetic susceptibility, as well as the scaling of the correlation length defined by ${\xi }^{\mathrm{-}1}$(x,T)=${\xi }^{\mathrm{-}1}$(x,0)+${\xi }^{\mathrm{-}1}$(0,T), all consistent with experiment. We suggest that for the electron-doped materials the single-hole ground corresponds to k=(π,0) quasiparticles; we show that the spin distortions generated by such carriers are short ranged. Then, we demonstrate the effect of this single-carrier difference in many-carrier ground states via exact diagonalization results by evaluating S(q) for up to four carriers in small clusters.