Many-body band renormalization in highly doped graphene
Date:
The extreme simplicity of its electronic structure has affirmed graphene as an ideal testbed for the demonstration of many-body renormalization effects on band structure. In this talk I will propose: 1) an undisputable experimental demonstration of the electron-phonon origin of the kink at 170 meV; 2) a demystification of the band flattening at the van-Hove singularity proximity [2]. Regarding the first case [1], I will show an energy shift towards the Fermi level of the “kink” associated to the electron-phonon coupling once the graphene is made of only 13C isotope rather than 12C. Such an energy shift is in excellent agreement with the expected softening of the phonon energy distribution due to the isotope substitution. Apart from providing an indisputable experimental proof of the electron-phonon coupling origin of this “kink”, I will discuss the experimental accuracy achievable with a proper robust analysis framework applied to the experimental data. For the second case [2], I will present an alternative interpretation for the highly doped graphene band flattening once the Fermi level approaches the van-Hove singularity. By simulating the graphene spectral function from the density functional theory calculated bands, it is possible to demonstrate that the photoemission signal around the M point originates from the spectral function tail of the unoccupied band above the Fermi level. Such interpretation put forward the absence of any additional strong correlation effects at the van-Hove singularity proximity, reconciling the mean field description of the graphene band structure even in the highly doped scenario.
[1] F. Bisti, et al., Phys. Rev. B 103, 035119 (2021). [2] M. Jugovac, et al., Phys. Rev. B 105, L241107 (2022).