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Tuesday, 04 April, 2017

Electronic interactions and noninvasive manipulations of 2D materials

Prof. Tim Wehling, Institute for Theoretical Physics, University of Bremen

Speaker: Opens external link in new windowProf. Tim Wehling, Electronic structure and correlated nanosystems, Institute for Theoretical Physics, University of Bremen

Time: Tuesday, 4 April 2017, 16:15h

Venue: Seminar room EG 0.001, Zentrum für Nanotechnologie und Nanomaterialien, Am Coulombwall 4a, 85748 Garching

 

Abstract (Initiates file downloadDownload):

Coulomb and electron-phonon interactions largely shape the electronic and optical properties of 2d materials. They affect band gaps and excitons in 2d semiconductors like MoS2 and lead to a competition of different metallic, insulating and superconducting phases in nominally metallic 2d materials like NbSe2 or TaS2. We discuss which of these effects can be manipulated by external screening and hybridization.

First, we consider 2d semiconducting monolayers in a dielectric environment and reveal a two-faced nature of interaction effects leading to a complex interplay of band gap changes and exciton binding effects. We show how this interplay leads to the prospect of trapping and guiding of excitations by means of tailor-made dielectric substrates.

Afterwards, we analyze how correlated electronic states in materials like NbSe2 or TaS2 change upon going from bulk to monolayers. We show that superconducting states in these materials are surprisingly robust against variations in external screening but that they are very sensitive to hybridization effects with neighboring layers and substrates. We introduce the concept of pseudodoping which appears to be ubiquitous in metallic 2d systems.

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