We study the spectral function of the homogeneous electron gas using many-body perturbation theory and the cumulant expansion. We compute the angle-resolved spectral function based on the GW approximation and the `GW plus cumulant' approach. In agreement with previous studies, the GW spectral function exhibits a spurious plasmaron peak at energies 1.5$ω_{\rm pl}$ below the quasiparticle peak, $ω_{\rm pl}$ being the plasma energy. The GW plus cumulant approach, on the other hand, reduces significantly the intensity of the plasmon-induced spectral features and renormalizes their energy relative to the quasiparticle energy to $ω_{\rm pl}$. Consistently with previous work on semiconductors, our results show that the HEG is characterized by the emergence of plasmonic polaron bands, that is, broadened replica of the quasiparticle bands, red-shifted by the plasmon energy.
Using state-of-the-art many-body calculations based on the `GW plus cumulant' approach, we show that electron-plasmon interactions lead to the emergence of plasmonic polaron bands in the band structures of common semiconductors. Using silicon and group IV transition metal dichalcogenide monolayers (AX2 with A=Mo,W and X=S,Se) as prototypical examples, we demonstrate that these new bands are a general feature of systems characterized by well defined plasmon resonances. We find that the energy vs. momentum dispersion relations of these plasmonic structures closely follow the standard valence ban…
The experimental unexpected large Seebeck coefficient in SrTiO3 (STO) cannot be reproduced theoretically by the conventional Bloch-Boltzmann transport with electron-phonon coupling calculated perturbatively, indicating a failure of Fermi liquid picture in STO and ill-treatment of polaronic states. Starting from many-body interaction picture, the polaronic states can be precisely described by the method of cumulant expansion of retarded Green's function. By applying Kubo-Greenwood method, we found that the mysterious Seebeck coefficient can be fully described by a combination of polarons and Fe…
Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；Korea Institute of Science and Technology（韩国科学技术院）；Kangwon National University（江原国立大学）；Chinese Academy of Sciences（中国科学院）；University of Chinese Academy of Sciences（中国科学院大学）；Pohang University of Science and Technology（浦项科技大学）；Korea Basic Science Institute (KBSI)（韩国基础科学研究所）；Pusan National University（釜山国立大学）；Stanford University（斯坦福大学）；SLAC National Accelerator Laboratory（SLAC国家加速器实验室）；Korea Institute of Energy Technology（韩国能源技术研究院）
We report experimental and theoretical evidence of strong electron-plasmon interaction in n-doped single-layer MoS2. Angle-resolved photoemission spectroscopy (ARPES) measurements reveal the emergence of distinctive signatures of polaronic coupling in the electron spectral function. Calculations based on many-body perturbation theory illustrate that electronic coupling to two-dimensional (2D) carrier plasmons provides an exhaustive explanation of the experimental spectral features and their energies. These results constitute compelling evidence of the formation of plasmon-induced polaronic qua…
Nonperturbative quantum theory of multiplasmonic electron emission from surfaces: Gauge-specific cumulant expansions vs. Volkov ansatz over plasmonic coherent states
We investigate the spectroscopic fingerprints of electron-plasmon coupling in integrated (PES) and angle-resolved photoemission spectroscopy (ARPES). To account for electron-plasmon interactions at a reduced computational cost, we derived the plasmonic polaron model, an approach based on the cumulant expansion of many-body perturbation theory that circumvents the calculation of the GW self-energy. Through the plasmonic polaron model, we predict the complete spectral functions and the effects of electron-plasmon coupling for Si, Ge, GaAs, and diamond. Si, Ge, and GaAs exhibit well-defined plasm…
Electron-boson interaction is fundamental to a thorough understanding of various exotic properties emerging in many-body physics. In photoemission spectroscopy, photoelectron emission due to photon absorption would trigger diverse collective excitations in solids, including the emergence of phonons, magnons, electron-hole pairs, and plasmons, which naturally provides a reliable pathway to study electron-boson couplings. While fingerprints of electron-phonon/-magnon interactions in this state-of-the-art technique have been well investigated, much less is known about electron-plasmon coupling, a…
The electron-phonon interaction causes thermal and zero-point motion shifts of electron quasiparticle (QP) energies $ε_k(T)$. Other consequences of interactions, visible in angle-resolved photoemission spectroscopy (ARPES) experiments, are broadening of QP peaks and appearance of sidebands, contained in the electron spectral function $A(k,ω)=-{\Im m}G_R(k,ω) /π$, where $G_R$ is the retarded Green's function. Electronic structure codes (e.g. using density-functional theory) are now available that compute the shifts and start to address broadening and sidebands. Here we consider MgO and LiF, and…
Predicting the electrical properties of organic molecular crystals (OMCs) is challenging due to their complex crystal structures and electron-phonon (e-ph) interactions. Charge transport in OMCs is conventionally categorized into two limiting regimes $-$ band transport, characterized by weak e-ph interactions, and charge hopping due to localized polarons formed by strong e-ph interactions. However, between these two limiting cases there is a less well understood intermediate regime where polarons are present but transport does not occur via hopping. Here we show a many-body first-principles ap…
In materials with strong electron-phonon ($e$-ph) interactions, the electrons carry a phonon cloud during their motion, forming quasiparticles known as polarons. Predicting charge transport and its temperature dependence in the polaron regime remains an open challenge. Here, we present first-principles calculations of charge transport in a prototypical material with large polarons, SrTiO$_{3}$. Using a cumulant diagram-resummation technique that can capture the strong $e$-ph interactions, our calculations can accurately predict the experimental electron mobility in SrTiO$_{3}$ between 150$-$30…
In polar semiconductors and insulators, the Fröhlich interaction between electrons and long-wavelength longitudinal optical phonons induces a many-body renormalization of the carrier effective masses and the appearence of characteristic phonon sidebands in the spectral function, commonly dubbed 'polaron satellites'. The simplest model that captures these effects is the Fröhlich model, whereby electrons in a parabolic band interact with a dispersionless longitudinal optical phonon. The Fröhlich model has been employed in a number of seminal papers, from early perturbation-theory approaches to m…
Polarons are quasi-particles made from electrons interacting with vibrations in crystal lattices. They derive their name from the strong electron-vibration polar interaction in ionic systems, that induces associated spectroscopic and optical signatures of such quasi-particles in these materials. In this paper, we focus on diamond, a non-polar crystal with inversion symmetry which nevertheless shows characteristic signatures of polarons, better denoted "nonpolarons" in this case. The polaronic effects are produced by short-range crystal fields with only a small influence of long-range quadrupol…
I propose a path integral description of the Su-Schrieffer-Heeger Hamiltonian, both in one and two dimensions, after mapping the real space model onto the time scale. While the lattice degrees of freedom are classical functions of time and are integrated out exactly, the electron particle paths are treated quantum mechanically. The method accounts for the variable range of the electronic hopping processes. The free energy of the system and its temperature derivatives are computed by summing at any $T$ over the ensemble of relevant particle paths which mainly contribute to the total partition f…
