paper

Chebyshev pseudosite matrix product state approach for the spectral functions of electron-phonon coupling systems

arXiv:2210.09208 · doi:10.1103/PhysRevResearch.5.023026

Abstract

The electron-phonon (-ph) coupling system often has a large number of phonon degrees of freedom, whose spectral functions are numerically difficult to compute using matrix product state (MPS) formalisms. To solve this problem, we propose a new and practical method that combines the Chebyshev MPS and the pseudosite density matrix renormalization group (DMRG) algorithm. The Chebyshev vector is represented by a pseudosite MPS with global fermion symmetry, which maps bosonic degrees of freedom onto pseudosites, each with two states. This approach can handle arbitrary -ph coupling Hamiltonians where pseudosite DMRG performs efficiently. We use this method to study the spectral functions of the doped extended Hubbard-Holstein model in a regime of strong Coulomb repulsion, which has not been studied extensively before. Key features of the excitation spectra are captured at a modest computational cost. Our results show that weak extended -ph couplings can increase the spectral weight of the holon-folding branch at low phonon frequencies, in agreement with angle-resolved photoemission observations on one-dimensional (1D) cuprates.

12 pages, 8 figures, new results added

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