Biexciton fine structure in monolayer transition metal dichalcogenides. Issue 12 (December 2018)

• Record Type: Journal Article
• Authors: Steinhoff, Alexander; Florian, Matthias; Singh, Akshay; Tran, Kha; Kolarczik, Mirco; Helmrich, Sophia; Achtstein, Alexander; Woggon, Ulrike; Owschimikow, Nina; Jahnke, Frank; Li, Xiaoqin
• Is Part Of: Nature physics. Volume 14:Issue 12(2018)
• Page Start: 1199
• Page End: 1204
• Publication Date: 2018-12
• Subjects: Physics -- Periodicals; 530.05
• DOI: 10.1038/s41567-018-0282-x
• Languages: English
• ISSNs: 1745-2473

Abstract

Abstract The optical properties of atomically thin transition metal dichalcogenide (TMDC) semiconductors are shaped by the emergence of correlated many-body complexes due to strong Coulomb interaction. Exceptional electron–hole exchange predestines TMDCs to be used to study fundamental and applied properties of Coulomb complexes such as valley depolarization of excitons and fine-structure splitting of trions. Biexcitons in these materials are less well understood and it has been established only recently that they are spectrally located between excitons and trions. Here we show that biexcitons in monolayer TMDCs exhibit a distinct and rich fine structure on the order of millielectronvolts due to electron–hole exchange. Ultrafast pump–probe experiments on monolayer WSe2 reveal decisive biexciton signatures and a fine structure in excellent agreement with a microscopic theory. We provide a pathway to understand the complex spectral structure of higher-order Coulomb complexes in TMDCs going beyond the usual classification scheme in terms of four-particle configurations. Biexcitons play an important role in determining the optical properties of transition metal dichalcogenide monolayers, but their precise structure is poorly understood. Using a combination of ultrafast spectroscopy and theory, the origin of their fine structure is revealed.