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arXiv · 1510.07454

Finite-size effects in Luther-Emery phases of Holstein and Hubbard models

J. Greitemann·S. Hesselmann·S. Wessel·F. F. Assaad·M. Hohenadler
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Abstract

The one-dimensional Holstein model and its generalizations have been studied extensively to understand the effects of electron-phonon interaction. The half-filled case is of particular interest, as it describes a transition from a metallic phase with a spin gap due to attractive backscattering to a Peierls insulator with charge-density-wave (CDW) order. Our quantum Monte Carlo results support the existence of a metallic phase with dominant power-law charge correlations, as described by the Luther-Emery fixed point. We demonstrate that for Holstein and also for purely fermionic models the spin gap significantly complicates finite-size numerical studies, and explains inconsistent previous results for Luttinger parameters and phase boundaries. On the other hand, no such complications arise in spinless models. The correct low-energy theory of the spinful Holstein model is argued to be that of singlet bipolarons with a repulsive, mutual interaction. This picture naturally explains the existence of a metallic phase, but also implies that gapless Luttinger liquid theory is not applicable.

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J. Greitemann, S. Hesselmann, S. Wessel, F. F. Assaad, M. Hohenadler. 2015-12-28. Finite-size effects in Luther-Emery phases of Holstein and Hubbard models. https://doi.org/10.1103/physrevb.92.245132

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