Affiliation:
1. Nanjing University
2. Nanyang Technological University
3. CNR NANOTEC
4. Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University
5. National University of Singapore
6. National Institute for Materials Science
7. National Institute for Materials Science, Tsukuba, Ibaraki
8. Tsinghua University
Abstract
Abstract
Energy transfer is a ubiquitous phenomenon that delivers energy from a blue-shifted emitter to a red-shifted absorber, which has enabled plentiful photonic applications of light-emitting diodes (LEDs), lasers, solar cells, and display devices1–5. The fast-emerging two-dimensional (2D) semiconductors offer unique opportunities for exploring new energy transfer mechanisms in the atomic-scale limit enabled by confined geometry and van der Waals architectures, which transcend the conventional Förster and Dexter types. Herein, we have successfully designed and constructed a planar optical microcavity-confined MoS2/hBN/WS2 heterojunction, which realizes the strong coupling among donor exciton, acceptor exciton, and cavity photon mode for the first time. Such a configuration demonstrates the unconventional energy transfer via ultrafast polariton relaxation, leading to the brightening of MoS2 neutral exciton with a record-high enhancement factor of ~ 440, i.e., two-order-of-magnitude higher than the data reported to date. A short characteristic time of ~ 1.3 ps is extracted by setting up a high-resolution k-space transient-reflectivity spectroscopy. This ultrafast polariton relaxation is attributed to the significantly enhanced intra- and inter-branch exciton-exciton scattering to overcome the hot phonon bottleneck effect, as revealed by theoretical calculation with coupled rate equations. Our study not only opens a new direction of microcavity 2D semiconductor heterojunctions for high-brightness ultrafast polaritonic light sources, but also provides a new paradigm to study the ultrafast polariton carrier dynamics.
Publisher
Research Square Platform LLC