TY  - JOUR
A1  - Nitsche, Wolfgang H.
A1  - Kim, Na Young
A1  - Roumpos, Georgios
A1  - Schneider, Christian
A1  - Höfling, Sven
A1  - Forchel, Alfred
A1  - Yamamoto, Yoshihisa
T1  - Spatial correlation of two-dimensional bosonic multimode condensates
JF  - Physical Review A
N2  - The Berezinskii-Kosterlitz-Thouless (BKT) theorem predicts that two-dimensional bosonic condensates exhibit quasi-long-range order which is characterized by a slow decay of the spatial coherence. However previous measurements on exciton-polariton condensates revealed that their spatial coherence can decay faster than allowed under the BKT theory, and different theoretical explanations have already been proposed. Through theoretical and experimental study of exciton-polariton condensates, we show that the fast decay of the coherence can be explained through the simultaneous presence of multiple modes in the condensate.
KW  - Exciton-polariton condensate
KW  - Long-range order
KW  - Microcavity
KW  - Vortices
KW  - Systems
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-188897
VL  - 93
IS  - 5
ER  - 
TY  - JOUR
A1  - Plötz, P.-A.
A1  - Polyutov, S. P.
A1  - Ivanov, S. D.
A1  - Fennel, F.
A1  - Wolter, S.
A1  - Niehaus, T.
A1  - Xie, Z.
A1  - Lochbrunner, S.
A1  - Würthner, Frank
A1  - Kühn, O.
T1  - Biphasic aggregation of a perylene bisimide dye identified by exciton-vibrational spectra
JF  - Physical Chemistry Chemical Physics
N2  - The quantum efficiency of light emission is a crucial parameter of supramolecular aggregates that can be tuned by the molecular design of the monomeric species. Here, we report on a strong variation of the fluorescence quantum yield due to different phases of aggregation for the case of a perylene bisimide dye. In particular, a change of the dominant aggregation character from H- to J-type within the first aggregation steps is found, explaining the observed dramatic change in quantum yield. This behaviour is rationalised by means of a systematic study of the intermolecular potential energy surfaces using the time-dependent density functional based tight-binding (TD-DFTB) method. This provides a correlation between structural changes and a coupling strength and supports the notion of H- type stacked dimers and J-type stack-slipped dimers. The exciton-vibrational level structure is modelled by means of an excitonic dimer model including two effective vibrational modes per monomer. Calculated absorption and fluorescence spectra are found to be in reasonable agreement with experimental ones, thus supporting the conclusion on the aggregation behaviour.
KW  - Potential-energy curves
KW  - Simulations
KW  - Molecular-dynamics
KW  - Systems
KW  - Fluorescence
KW  - Sracking
KW  - Pathway
KW  - Dimers
KW  - State
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-187387
VL  - 18
IS  - 36
ER  -