Electron addition spectral functions of low-density polaron liquids

Abstract

Spectral functions are important quantities that contain a wealth of information about the quasiparticles of a system, and that can also be measured experimentally. For systems with electron-phonon coupling, good approximations for the spectral function are available only in the Migdal limit (at Fermi energies much larger than the typical phonon frequency, $E_F\gg \Omega$, requiring a large carrier concentration $x$) and in the single polaron limit (at $x=0$). Here we show that the region with $x\ll 1$ ($E_F<\Omega$) can also be reliably investigated with the Momentum Average (MA) variational approximation, which essentially describes the formation of a polaron above an inert Fermi sea. Specifically, we show that for the one-dimensional spinless Holstein model, the MA spectral functions compare favorably with those calculated using variationally exact density matrix renormalization group simulations (DMRG) evaluated directly in frequency-space, so long as $x<0.1$ and the adiabaticity ratio $\Omega /t>0.5$. Unlike in the Migdal limit, here 'polaronic physics' emerges already at moderate couplings. The relevance of these results for a spinful low-$x$ metal is also discussed.

10 pages, 3 figures, Submission to SciPost

References in corpus (13)

• Green's function of a dressed particle
• Polarons from first principles, without supercells
• The Green's Function of the Holstein Polaron
• Spectral Functions with the Density Matrix Renormalization Group: Krylov-space Approach for Correction Vectors
• Systematic improvement of the Momentum Average approximation for the Green's function of a Holstein polaron
• Diagrammatic Monte Carlo method for many-polaron problems
• Unified approach to polarons and phonon-induced band structure renormalization
• Charge-density-wave melting in the one-dimensional Holstein model
• Quantum dynamics simulation of intramolecular singlet fission in covalently linked tetracene dimer
• Interplay of charge, spin and lattice degrees of freedom on the spectral properties of the one-dimensional Hubbard-Holstein model
• Doping dependence of ordered phases and emergent quasiparticles in the doped Hubbard-Holstein model
• Root-N Krylov-space correction-vectors for spectral functions with the density matrix renormalization group
• Obstructions to odd-frequency superconductivity in Eliashberg theory

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