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Seminarium prof. Alexander Grüneis

11 maja 2017, czwartek, 13:15, sala G-1-09 "Electronic and vibrational properties of alkali metal functionalized layered materials"

11 maja 2017, czwartek, 13:15  (czas trwania: 60 minut)
Kampus UJ, Wydział FAIS, ul. S. Łojasiewicza 11, sala G-1-09
---  prof. Alexander Grüneis ( II. Physikalisches Institut, Universitat zu Köln, Germany ) :
"Electronic and vibrational properties of alkali metal functionalized layered materials"
Ionic functionalization of many layered materials by alkali and alkaline earth metals enables tuning of the charge carrier density into the superconducting regime. We investigate their electron energy band structure and spectral function with high-resolution angle-resolved photo emission spectroscopy (ARPES). For example, for Ca doped graphene this charge transfer can induce relatively large electron-phonon coupling constants of ~0.4 [1]. This provides experimental support for the possibility to achieve superconductivity in graphene mono layers at 1.5K. Indeed, superconductivity in Ca doped mono layer graphene was realized experimentally only recently [2]. Regarding ionic functionalization of related layered materials, we investigate the interaction of alkali metals with epitaxial mono layer boron nitride, graphene nanoribbons, and the bulk black phosphorous compounds [3]. While boron nitride does not accept electrons, the band gap of the latter two materials is sufficiently small so that a semiconductor to metal transition can be induced by ionic functionalization. The ARPES data of the quasi particle dispersion are complemented by ultra-high-vacuum Raman/luminescence spectra of functionalized 2D materials[4,5]. These are recorded with a homebuilt optical interface to a commercial Raman spectrometer. After a brief introduction to setup, the drastic changes in the Raman response upon doping is discussed.
[1] Fedorov, Grüneis Nature Comm. 5, 3257 (2014).
[2] Chapman et al. Scientific Reports 6, 23254 (2016).
[3] A. Sanna, A. V.Fedorov,A. Grüneis 2D Materials,3, 025031 (2016).
[4] Senkovskiy, Grüneis et al. Adv. Elect. Materials (2017) DOI: 10.1002/aelm.201600490
[5] Senkovskiy, Loosdrecht, Meerholz, Lindfors, Grüneis Nano Letters (2017) DOI: 10.1021/acs.nanolett.7b00147