Theory of electron-hole asymmetry in dopedCuO2planes

Abstract

The magnetic phase diagrams, and other physical characteristics, of the hole-doped La2 Sr Cu04 and electron-doped Ndq Ce Cu04 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 = ( -, -) quasiparticles, states that generate so-called Shraiman-Siggia long-ranged dipolar spin distortions via back6ow. 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 ( (z, T) = ( (z, O) + ( (O, T), all consistent with experiment. We suggest that for the electron-doped materials the single-hole ground state corresponds to k = (s, O) quasiparticles; we show that the spin distortions generated by such carriers are shortranged. 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. Consistent with experiment, for the hole-doped materials short-ranged incommensurate spin orderings are induced, whereas for the electron-doped system only commensurate spin correlations are found. Further, we propose that there is an important difference between the spatial distributions of mobile carriers for these two systems: for the hole-doped material the quasiparticles tend to stay far apart from one another, whereas for the electron-doped material we find tendencies consistent with the clustering of carriers, and possibly of low-energy Buctuations into an electronic phase-separated state. Phase separation in this material is consistent with the midgap states found by recent angle-resolved photoemission spectroscopy studies. Last, we propose the extrapolation of an approach based on the t-t'-J model to the hole-doped 123 system.

Asymmetry of the electron spectrum in hole-doped and electron-doped cuprates

“…This study also shows unambiguously that the energy scale of the quasiparticle band is controlled by the magnetic interaction J. In particular, the electron-hole asymmetry in hole-doped and electron-doped cuprates has been discussed based on numerically exact diagonalization methods 21 , it is shown that the electron-hole asymmetry comes from the coupling of the charge carriers with the spin background. Moreover, many authors 22,23 suggest that the unusual electron spectrum in doped cuprates is a natural consequence of the charge-spin separation (CSS).…”

“…This renormalization due to the strong interaction is then responsible for the unusual electron quasiparticle spectrum and production of the flat band. On the other hand, although t ′ does not change spin configuration, the interplay of t ′ with t and J causes a further weakening of the AF spin correlation for the hole doping, and enhancing the AF spin correlation for the electron doping 21 , which shows that the AF spin correlations in the electron doping is stronger than these in the hole-doped side, and leads to the asymmetry of the electron spectrum in hole-doped and electron-doped cuprates. This is why t ′ term plays an important role in explaining the difference between electron and hole doping.…”

Comparison of 32-site exact-diagonalization results and ARPES spectral functions for the antiferromagnetic insulatorSr2CuO2Leung1, Wells2, Gooding3 1997Phys. Rev. BSelf Cite748710View full textAdd to dashboardCite

“…5 Instead, at the very least hoppings beyond near neighbor must be added to the t-J model. [6][7][8][9][10] The recognition of the importance of further hoppings has also been obtained in a spin-density-wave treatment of the one-band Hubbard model. 11 Work on the more physically plausible three-band model has shown that this model is superior in reproducing the experimental band structure in all regions of the first Brillouin zone.…”

Charge-Density-Excitation Spectrum in the t–t′–J–V Model

“…We have found that the nearest-neighbor Coulomb repulsion V plays a crucial role to understand the low-energy charge excitations around q = (0, 0) especially in a model calculation for e-cuprates, because e-cuprates are expected to be close to PS [15][16][17][18] .…”

“…These different theoretical conclusions could be understood consistently by considering the well-known insight that e-cuprates are expected to be closer to phase separation (PS) than h-cuprates as shown by various theoretical studies [15][16][17][18] . However, charge excitations associated with PS are hardly known even theoretically.…”