Ultrafast transition between exciton phases in van der Waals heterostructures
Inledande text i tidskrift, 2019

© 2019, The Author(s), under exclusive licence to Springer Nature Limited. Heterostructures of atomically thin van der Waals bonded monolayers have opened a unique platform to engineer Coulomb correlations, shaping excitonic1–3, Mott insulating4 or superconducting phases5,6. In transition metal dichalcogenide heterostructures7, electrons and holes residing in different monolayers can bind into spatially indirect excitons1,3,8–11 with a strong potential for optoelectronics11,12, valleytronics1,3,13, Bose condensation14, superfluidity14,15 and moiré-induced nanodot lattices16. Yet these ideas require a microscopic understanding of the formation, dissociation and thermalization dynamics of correlations including ultrafast phase transitions. Here we introduce a direct ultrafast access to Coulomb correlations between monolayers, where phase-locked mid-infrared pulses allow us to measure the binding energy of interlayer excitons in WSe2/WS2 hetero-bilayers by revealing a novel 1s–2p resonance, explained by a fully quantum mechanical model. Furthermore, we trace, with subcycle time resolution, the transformation of an exciton gas photogenerated in the WSe2 layer directly into interlayer excitons. Depending on the stacking angle, intra- and interlayer species coexist on picosecond scales and the 1s–2p resonance becomes renormalized. Our work provides a direct measurement of the binding energy of interlayer excitons and opens the possibility to trace and control correlations in novel artificial materials.

Författare

Philipp Merkl

Universität Regensburg

F. Mooshammer

Universität Regensburg

Philipp Steinleitner

Universität Regensburg

A. Girnghuber

Universität Regensburg

K. Q. Lin

Universität Regensburg

P. Nagler

Universität Regensburg

J. Holler

Universität Regensburg

C. Schuller

Universität Regensburg

J. M. Lupton

Universität Regensburg

T. Korn

Universität Rostock

Universität Regensburg

Simon Ovesen

Chalmers, Fysik, Kondenserade materiens teori

Samuel Brem

Chalmers, Fysik, Kondenserade materiens teori

Ermin Malic

Chalmers, Fysik, Kondenserade materiens teori

R. Huber

Universität Regensburg

Nature Materials

1476-1122 (ISSN) 1476-4660 (eISSN)

Vol. 18 7 691-696

Ämneskategorier

Atom- och molekylfysik och optik

Annan fysik

Den kondenserade materiens fysik

DOI

10.1038/s41563-019-0337-0

PubMed

30962556

Mer information

Senast uppdaterat

2019-07-02