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In high-temperature cuprate superconductors, the anti-ferromagnetic spin fluctuations are thought to have a very important role in naturally producing an attractive interaction between the electrons in the d-wave channel. The connection between superconductivity and spin fluctuations is expected to be especially consequential at the overdoped end point of the superconducting dome. In some materials, that point seems to coincide with a Lifshitz transition, where the Fermi surface changes from the hole-like centered at to the electron-like, centered at the Γ point causing a loss of large momentum anti-ferromagnetic fluctuations. Here, we study the doping dependence of the electronic structure of Bi1.8Pb0.4Sr2CuO in angle-resolved photoemission and find that the superconductivity vanishes at lower doping than that at which the Lifshitz transition occurs. This requires a more detailed re-examination of a spin fluctuation scenario. [ABSTRACT FROM AUTHOR]

In the present work, we investigate the electronic structure of the two-dimensional ferromagnet Cr2Ge2Te6 by photoemission spectroscopy and ab initio calculations. Our results demonstrate the presence of multi-hole–type bands in the vicinity of the Fermi level indicating that the material can support high electrical conductivity by manipulating the chemical potential. Also, our photon energy-dependent angle-resolved photoemission experiment shows that several of the hole bands exhibit weak dispersion with varied incident photon energy providing experimental signature for the two-dimensional nature of Cr2Ge2Te6. Thereby, these findings can pave the way for further studies towards the application of Cr2Ge2Te6 in electronic devices. [ABSTRACT FROM AUTHOR]