Abstract
Carrier doping by the electric field effect has emerged as an ideal route for monitoring many-body physics in two-dimensional materials where the Fermi level is tuned so that the strength of the interactions can also be scanned. The possibility of systematic doping together with high resolution photoemission has allowed to uncover a genuinely many-body electron spectrum in single-layer MoS2 transition metal dichalcogenide, resolving three clear quasi-particle states, where only one should be expected if the electron–phonon interaction vanished. Here, we combine first-principles and consistent complex plane analytic approaches and bring into light the physical origin of the two gaps and the three quasi-particle bands which are unambiguously present in the photoemission spectrum. One of these states, though being strongly interacting with the accompanying virtual phonon cloud, presents a notably long lifetime which is an appealing property when trying to understand and take advantage of many-body interactions to modulate transport properties.
Highlights
Carrier doping by the electric field effect has emerged as an ideal route for monitoring manybody physics in two-dimensional materials where the Fermi level is tuned so that the strength of the interactions can be scanned
Our ab initio calculations of the electron spectral function including electron–phonon effects together with the complex plane analysis of the quasiparticle poles rule out that hypothesis, and show that the singular band splitting observed in angle-resolved photoemission spectroscopy (ARPES) experiments can be explained by three coexisting quasiparticle states, one of which has an exceptionally long lifetime
The density of states (DOS) increases step-like as the 2D quasi-parabolic conductionbands get populated, showing a noticeable enhancement with the filling of the Q (Q′) bands (Fig. 2a), the main consequence being that, among all the possible intervalley scattering channels connecting the Fermi sheets, the phonon modes with momentum q 1⁄4 M are the ones dominating the whole electron–phonon coupling (Fig. 2b)
Summary
Carrier doping by the electric field effect has emerged as an ideal route for monitoring manybody physics in two-dimensional materials where the Fermi level is tuned so that the strength of the interactions can be scanned. We combine first-principles and consistent complex plane analytic approaches and bring into light the physical origin of the two gaps and the three quasi-particle bands which are unambiguously present in the photoemission spectrum One of these states, though being strongly interacting with the accompanying virtual phonon cloud, presents a notably long lifetime which is an appealing property when trying to understand and take advantage of many-body interactions to modulate transport properties. For electrons above ω0 the emission of phonons is allowed, the effect being that virtual processes are less probable in favor of real emission of phonons leading to a decreasing of their lifetime and effective mass This idealized picture will be useful for understanding the more intricate situation in MoS2 and questions the simple view about quasi-particle properties themselves, since the interaction with phonons produces two different electron states with radically different properties. Our ab initio calculations of the electron spectral function including electron–phonon effects together with the complex plane analysis of the quasiparticle poles rule out that hypothesis, and show that the singular band splitting observed in ARPES experiments can be explained by three coexisting quasiparticle states, one of which has an exceptionally long lifetime
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