Optical properties of electrostatically-doped monolayer semiconductors
Abstract
Research in two-dimensional atomic layers is a leading frontier in material science and engineering. The Van der Waals interlayer bonding between two-dimensional crystals enables unprecedented materials opportunities and it removes usual fabrication rules that require good lattice match between different materials (e.g., a layer by layer growth in molecular beam epi-taxy). In the case of single layer graphene, it has become clear that the lack of sizable bandgap energy precludes its usage in eld-eect transistors. In the case of nascent monolayer transition-metal dichalcogenides, on the other hand, the band gap energies are sizable and the exceptionally strong light-matter interaction provides exciting possibilities to realize opto-electronic devices. Compared with typical semiconductors, excitons (electron-hole pairs) are strongly bound in these materials due to relatively large effective masses of electrons and holescombined with the impeded Coulomb screening in genuine two-dimensional systems.This project will focus on theoretical analysis of the optical properties of monolayer WSe2. In addition to having unprecedentedly rich photoluminescence spectrum, this monolayer semi-conductor reveals exotic many-body interactions between exciton complexes and the Fermi sea when it is electrostatically doped with electrons. We plan to investigate the microscopic ori-gin of these many-body interactions, trying to understand if they stem from long-wavelengthcollective spin excitations that couple between the optically bright and dark exciton states, or from correlated states wherein three-body bound states (trions) are coupled to Coulomb holes in Fermi sea. In addition to investigation of many-body interactions, we will study the dynam-ics of exciton formation and energy relaxation during photoexcitation. We will develop Monte Carlo simulations that can help understand how to improve the luminescence quantum yield through exciton-electron exchange scattering, while suppressing non-radiative Auger processes of excitons and trions.While the proposed scientific research is fundamental in nature, the gained knowledge from this study will have important impact on the design of optoelectronic devices such as lasers with ultra-low power threshold, far- infrared detectors, and transistor-like optical multiplexers that harness the many-body interaction between excitons and electrons.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2021
- Source ID
- N000142112448
Entities
People
- Hanan Dery
Organizations
- Office of Naval Research
- United States Navy
- University of Rochester