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arXiv · 0803.0567

The isotope effect in the Hubbard model with local phonons

Alexandru Macridin·Mark Jarrell
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Abstract

The isotope effect (IE) in the two-dimensional Hubbard model with Holstein phonons is studied using the dynamical cluster approximation with quantum Monte Carlo. At small electron-phonon (EP) coupling the IE is negligible. For larger EP coupling there is a large and positive IE on the superconducting temperature that decreases with increasing doping. A significant IE also appears in the low-energy density of states, kinetic energy and charge excitation spectrum. A negligible IE is found in the pseudogap and antiferromagnetic (AF) properties at small doping whereas the AF susceptibility at intermediate doping increases with decreasing phonon frequency $ω_0$. This IE stems from increased polaronic effects with decreasing $ω_0$. A larger IE at smaller doping occurs due to stronger polaronic effects determined by the interplay of the EP interaction with stronger AF correlations. The IE of the Hubbard-Holstein model exhibits many similarities with the IE measured in cuprate superconductors.

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Alexandru Macridin, Mark Jarrell. 2008-03-05. The isotope effect in the Hubbard model with local phonons. https://doi.org/10.1103/physrevb.79.104517

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