Electron-phonon coupling and spin-charge separation in one-dimensional Mott insulators

Abstract

We examine the single-particle excitation spectrum in the one-dimensional Hubbard-Holstein model at half-filling by performing the dynamical density matrix renormalization group (DDMRG) calculation. The DDMRG results are interpreted as superposition of spectra for a spinless carrier dressed with phonons. The superposition is a consequence of robustness of the spin-charge separation against electron-phonon coupling. The separation is in contrast to the coupling between phonon and spin degrees of freedom in two-dimensional systems. We discuss implication of the results of the recent angle-resolved photoemission spectroscopy measurements on SrCuO2.PACS numbers: 71.10. Fd, 74.72.Jt The interplay between electron correlation and electron-phonon coupling is one of the hot topics in the field of strongly correlated electron systems such as high-T c cuprates. Particularly in an electron-removal process from the Mott insulators, the electron-phonon coupling occurs due to charge imbalance around a created hole. Thus, the angle-resolved photoemission spectroscopy (ARPES) is a direct tool, and observes a quasiparticle dressed with phonons [1]. For the twodimensional (2D) insulating cuprates, the ARPES experiments have revealed a broad low-energy peak that is interpleted as a result of disappearance of the quasiparticle weight due to the coupling [2,3,4].The quasiparticle in the 2D systems is not only dressed with phonon cloud, but also dressed with antiferromagnetic (AF) spin fluctuation. Thus, the effect of phonon on the spectrum is affected by the spin configuration of the background. However, in one-dimensional (1D) correlated electron systems, a photohole created by ARPES decays into spinon and holon due to the spin-charge separation [5]. Therefore, the effect of phonon on the spectrum strongly depends on whether the spin-charge separation is robust against the electron-phonon coupling. In this Letter, we examine the effect of phonon on the singleparticle excitation spectrum in 1D Mott insulators.Theoretically, the Hubbard-Holstein model is a basic model to study the interplay between electron correlation and electron-phonon coupling in cuprates [6,7]. However, we have only limited information on the singleparticle excitation spectrum in this model [4,8,9,10,11,12,13]. This is because it is hard to treat the infinite phononic degrees of freedom and electron correlation on an equal footing. In order to overcome the difficulty, we apply the dynamical density matrix renormalization group (DDMRG) method to the calculation of the spec- * Present adress:Department of Physics, Tohoku University, Sendai 980-8578, Japan; Electronic address: matsueda@cmpt.phys.tohoku.ac.jp tra in the half-filled systems.We find the following four characteristic features in the single-particle excitation spectrum: (i) a dip at highbinding energy side of the spinon branch, (ii) broad holon branch, (iii) decrease of the spectral weight of the spinon branch, and (iv) slight enhancement of the weight at lowbinding energy side of the spinon branch. ...

Interplay of charge, spin, and lattice degrees of freedom in the spectral properties of the one-dimensional Hubbard-Holstein model

“…In this case, we reproduce the results of Ref. 19 finding the characteristic spectral peak-dip-hump structure.…”

“…Within this model, the electronic spectral properties have been studied by Ref. 19 and 20, where the adiabatic limit (phonon frequency smaller than the electronic hopping) is mostly analyzed at half electronic filling in the regime of weak to intermediate e-ph coupling. In the first paper, the authors use dynamical density matrix renormalization group (D-DMRG) and assess the robustness of SCS against e-ph coupling, interpreting the spectral function as a superposition spectra of spinless fermions dressed by phonons.…”

Phase diagram of the one-dimensional Hubbard-Holstein model at half and quarter filling

“…15 find the intermediate phase existing in a narrow region on both sides of the U eff = 0 line, while we find the intermediate phase only for U eff Ͻ 0. Several calculations of the single-particle spectral function are available for the HHM, [41][42][43] the spinless Holstein model, 44,45 as well as the d = ϱ studies previously mentioned. In Ref.…”

Metallicity in the half-filled Holstein-Hubbard model

“…In this respect the one-dimensional (1D) Holstein 1 -Hubbard 2 model (HHM) is particularly rewarding to study. [5][6][7][8][9][10][11][12][13][14] It accounts for a tight-binding electron band, an intra-site Coulomb repulsion between electrons of opposite spin, a local coupling of the charge carriers to optical phonons, and the energy of the phonon subsystem in harmonic approximation: 343 (1959)) has been studied extensively as a paradigmatic model for polaron formation in the low-density limit. For commensurate band fillings the coupling to the lattice supports charge ordering.…”