Optical fingerprint of dark 2p-states in transition metal dichalcogenides
Artikel i vetenskaplig tidskrift, 2017

Atomically thin transition metal dichalcogenides exhibit a remarkably strong Coulomb interaction. This results in a fascinating many-particle physics including a variety of bright and dark excitonic states that determine optical and electronic properties of these materials. So far, the impact of dark states has remained literally in the dark to a large extent, since a measurement of these optically forbidden states is very challenging. Here we demonstrate a strategy to measure a direct fingerprint of dark states even in standard linear absorption spectroscopy. We present a microscopic study on bright and dark higher excitonic states in the presence of disorder for the exemplary material of tungsten disulfide (WS2). We show that the geometric phase cancels the degeneration of 2s and 2p states and that a significant disorder-induced coupling of these bright and dark states offers a strategy to circumvent optical selection rules. As a proof, we show a clear fingerprint of dark 2p states in the absorption spectrum of WS2. The predicted softening of optical selection rules through exciton-disorder coupling is of general nature and therefore applicable to related two-dimensional semiconductors.

dark exciton

excitons

TMD

excitonic absorption spectrum

photoluminescence

monolayer mos2

exciton

Materials Science

wse2

linear optic

graphene

Författare

Gunnar Berghäuser

Chalmers, Fysik, Kondenserade materiens teori

A. Knorr

Technische Universität Berlin

Ermin Malic

Chalmers, Fysik, Kondenserade materiens teori

2D Materials

2053-1583 (eISSN)

Vol. 4

Drivkrafter

Hållbar utveckling

Ämneskategorier

Fysik

DOI

10.1088/2053-1583/4/1/015029